WO2011033664A1 - High-frequency element - Google Patents

Abstract

A compact high-frequency element makes it possible to transmit a plurality of desired frequencies and attenuate unnecessary band components. The high-frequency element comprises: a first electrode (10); a second electrode (12) provided above the first electrode; a plurality of magnetoresistive effect elements (20₁ to 20_n) provided between the first electrode and the second electrode and each having a magnetization fixed layer (21) in which the direction of magnetization is fixed, a magnetization free layer (23) in which magnetization oscillation is excited depending on the flowing direction and strength of spin injection current, and a spacer layer (22) provided between the magnetization fixed layer and the magnetization free layer, wherein the cross-sectional areas of the magnetization free layers are different from each other; and an input terminal (32) for receiving a signal and an output terminal (34) for outputting a signal, both of which are separately provided on the second electrode.

Description

High frequency element

The present invention relates to a high-frequency element that attenuates a signal of an unnecessary band frequency from high-frequency power.

The use of high-frequency bands for wireless communication is progressing, and wireless LAN (Local Area Network) and Bluetooth wireless communication are beginning to be used in the home. As a result, the connection of AV devices can be made cordless or the devices can be operated in conjunction with each other. In storefronts, RFID (Radio Frequency IDentification) is spreading from the viewpoint of product inventory management and security. Here, there are a method of managing security by combining a gate type antenna and an RFID tag, and a method of pasting a product information tag on a cardboard containing products and reading it with a handy reader and managing inventory. In wireless LAN, Bluetooth, and RFID, a 2 GHz band and a 5 GHz band are used, and a specific frequency within the band is allocated and used for each application. There is also wireless communication that uses UWB (Ultra Wide Band) band of 3.4 GHz to 4.8 GHz or 7.25 GHz to 10.25 GHz to distribute information to a plurality of frequencies while suppressing signal strength.

In wireless communications, the issue is how to suppress the effects of interference from radio waves in the adjacent frequency bands. In order to realize good communication quality without the user being aware of radio communication interference, it can be considered that a filter for attenuating a signal in an unnecessary frequency band is incorporated in each device as an effective solution.

By the way, antenna design is an important key in wireless communication. The antenna length is determined by the wavelength of the received radio wave. For example, the antenna length that can efficiently receive a 2 GHz radio wave is about 3.8 cm (1/4 wavelength) to 15 cm. The higher the radio wave, the shorter the antenna length can be designed. There are two antenna designs. One is a design in which a gain is given only to a specific band to be used. The other is an antenna shape that can receive radio waves in a wide frequency band assuming a plurality of uses, and an unnecessary band is attenuated by a filter. Whichever antenna is used, it is important to attenuate the frequency component of the unnecessary band from the received power.

There is a method of configuring a BEF (Band Elimination Filter (hereinafter also referred to as a trap filter) in an LC circuit in a filter that attenuates a frequency component of an unnecessary band from received power. However, an inductance L and a capacitance C have self-resonant frequencies, respectively. Therefore, the designed ideal frequency characteristics and actual filter characteristics have been difficult to shift, and because the filter is composed of L and C, the size is at least several mm square and has good attenuation characteristics. There was a problem in terms of making the filter small.

On the other hand, there is a method of configuring a BEF with a transmission line. A stub (open end) is connected in parallel between the input and output terminals. In this case, the input impedance when looking at the stub side is 0 at an odd multiple of the frequency component to be attenuated, and all the odd multiple frequencies are trapped. For this reason, there is a problem that it is very difficult to make a filter that transmits radio waves of RFID and UWB and attenuates other unnecessary bands.

On the other hand, it has been reported that a spin injection device is used as an example of a small filter that is assumed to be used such that the amount of input current is constant (see, for example, Patent Document 1). This small filter is a filter that limits the transmission band by using two spin injection elements connected in series and in parallel between the input and output terminals, and utilizing the fact that the spin injection elements have resonance at frequencies in the GHz band. However, according to the examination results of the present inventors, this filter has a problem that it is difficult to make a filter that attenuates a wide band when an unnecessary frequency component is attenuated.

In addition, metamaterials are known in which the refractive index is artificially changed by changing the metal structure to adjust the dielectric constant and permeability so that the resonance frequency is given to the GHz band and the THz band (non-patent document). Reference 1). As an example of an application using this metamaterial, it has been reported that metal coils having a diameter of less than 1 mm are periodically arranged to absorb electromagnetic waves in the vicinity of 5 GHz. However, according to the examination results of the inventors of the present application, in such a metamaterial, the resonance frequency is determined by the values of L and C due to the coil structure. In order to have a resonance frequency in the GHz band, the size of one coil has to be about several hundred microns, and there is a problem that the size is increased in order to configure a filter. Further, in order to increase the absorption efficiency of electromagnetic waves, it is necessary to arrange a plurality of coils, and the absorption efficiency and the in-plane occupation area have a trade-off relationship.

As described above, it is useful to have a high-frequency filter (high-frequency element) that is small in size and easy to match with peripheral circuits and can attenuate unnecessary band components while transmitting a plurality of desired frequencies. Conceivable. *

JP 2007-189686 A

The present invention has been made in consideration of the above circumstances, and provides a high-frequency element that is small in size and capable of attenuating unnecessary band components while transmitting a plurality of desired frequencies. *

The high-frequency device according to the first aspect of the present invention includes a first electrode, a second electrode provided on the first electrode, and the first electrode and the second electrode. A plurality of magnetoresistive effect elements provided, each magnetoresistive effect element having a magnetization pinned layer in which the magnetization direction is pinned, and magnetization free excited by magnetization vibration depending on the direction and strength of flow of the spin injection current A plurality of magnetoresistive elements having a layer, a spacer layer provided between the magnetization pinned layer and the magnetization free layer, and having different cross-sectional areas of the magnetization free layer, An input terminal for inputting a signal and an output terminal for outputting a signal are provided separately from each other on the second electrode.

The high-frequency element according to the second aspect of the present invention includes a first electrode, a second electrode provided on the first electrode, and a third electrode provided on the second electrode. A first magnetoresistive effect element group provided between the first electrode and the second electrode, each magnetoresistive effect element having a magnetization pinned layer having a magnetization direction fixed; A magnetization free layer excited by magnetization oscillation according to the direction and strength of the spin injection current, and a spacer layer provided between the magnetization pinned layer and the magnetization free layer, and the magnetization free layer A first magnetoresistive element group having different cross-sectional areas, and a second magnetoresistive element group provided between the second electrode and the third electrode, Each magnetoresistive element has a magnetization pinned layer in which the magnetization direction is fixed, and a direction in which the spin injection current flows. A magnetization free layer that is excited according to the magnetization vibration, and a spacer layer provided between the magnetization pinned layer and the magnetization free layer, wherein the magnetization free layer has a different cross-sectional area. And a second magnetoresistive element group.

According to the present invention, the unnecessary band component can be attenuated while transmitting a plurality of desired frequencies.

Sectional drawing which shows the high frequency filter of 1st Embodiment. The perspective view which shows the high frequency filter of 1st Embodiment. The figure which shows the frequency characteristic of the magnetoresistive effect element used for the high frequency filter of 1st Embodiment. The figure which shows the frequency characteristic of the high frequency filter of 1st Embodiment. FIGS. 5A to 5C are plan views showing an example of the arrangement of magnetoresistive elements. FIG. 6A is a cross-sectional view when the magnetization directions of the magnetization free layer and the magnetization pinned layer are substantially parallel to the film surface, and FIG. 6B shows the magnetization direction of the magnetization free layer and the magnetization pinned layer as the film surface. FIG. 6C is a cross-sectional view when the magnetization direction of the magnetization free layer is substantially parallel to the film surface and the magnetization direction of the magnetization pinned layer is substantially perpendicular to the film surface. . 7A to 7C are cross-sectional views showing the shape of the magnetization fixed layer. Sectional drawing which shows an example of a magnetoresistive effect element. The perspective view which shows the high frequency filter of 2nd Embodiment. The perspective view which shows the high frequency filter of 1st Example. The figure which shows the resonant frequency characteristic of the magnetoresistive effect element used for 1st Example. The figure which shows the frequency characteristic of the high frequency filter of 1st Example. The perspective view which shows the high frequency filter by the modification of 1st Example. The perspective view which shows the high frequency filter of 2nd Example. The perspective view which shows the high frequency filter of 3rd Example. The figure which shows the resonant frequency characteristic of the magnetoresistive effect element used for 3rd Example. The figure which shows the frequency characteristic of the high frequency filter of 3rd Example. The perspective view which shows the high frequency filter by the modification of 3rd Example. The perspective view which shows the high frequency filter of 4th Example. The perspective view which shows the high frequency filter of 5th Example. Sectional drawing which shows the high frequency filter of 6th Example. The figure which shows the precession frequency characteristic of the magnetoresistive effect element provided with the magnetization free layer which has magnetization parallel to a film surface. The figure which shows the frequency characteristic of the high frequency filter of one Embodiment. The figure which shows the frequency characteristic of the high frequency filter of one Embodiment. The figure which shows the precession frequency characteristic of the magnetoresistive effect element provided with the magnetization free layer which has magnetization perpendicular | vertical to a film surface. The figure which shows the frequency characteristic of the high frequency filter of one Embodiment. The figure which shows the frequency characteristic of the high frequency filter of one Embodiment. The figure which shows the precession frequency characteristic of the magnetoresistive effect element in which a magnetization free layer has magnetization parallel to a film surface, and a magnetization fixed layer has magnetization perpendicular | vertical to a film surface. The figure which shows the frequency characteristic of the high frequency filter of one Embodiment. The figure which shows the frequency characteristic of the high frequency filter of one Embodiment. FIG. 31A is a perspective view showing a high-frequency filter according to one embodiment, and FIG. 31B is a diagram showing transmission characteristics of the high-frequency filter according to one embodiment. FIG. 32A is a perspective view showing a high-frequency filter according to one embodiment, and FIG. 32B is a diagram showing transmission characteristics of the high-frequency filter according to one embodiment. The figure which shows the permeation | transmission characteristic of the high frequency filter of one Embodiment. FIG. 34A is a perspective view showing a high-frequency filter according to one embodiment, and FIG. 34B is a cross-sectional view showing the high-frequency filter according to one embodiment. FIG. 35A is a perspective view showing the high-frequency filter according to the embodiment, and FIG. 35B is a cross-sectional view showing the high-frequency filter according to the embodiment. The perspective view which shows the high frequency filter of one Embodiment. FIGS. 37A and 37B are perspective views showing a high-frequency filter according to an embodiment. 38 (a) and 38 (b) are perspective views showing a high-frequency filter according to an embodiment. FIGS. 39A and 39B are perspective views showing a high-frequency filter according to an embodiment. 40 (a) and 40 (b) are perspective views showing a high-frequency filter according to an embodiment. 41 (a) and 41 (b) are perspective views showing a high-frequency filter according to an embodiment. 42 (a) and 42 (b) are perspective views showing a high-frequency filter according to an embodiment. 1 is a circuit diagram of a transmission / reception system in which a high-frequency filter according to an embodiment is used. The circuit diagram of MIMO in which the high frequency filter of one Embodiment is used. 45 (a) and 45 (b) are perspective views showing a high-frequency filter according to an embodiment. 46 (a) and 46 (b) are perspective views showing a high-frequency filter according to an embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
A high-frequency filter according to a first embodiment of the present invention is shown in FIGS. FIG. 1 is a cross-sectional view of the high-frequency filter 1 of the present embodiment, and FIG. 2 is a perspective view.

The high-frequency filter 1 of this embodiment includes a plurality of magnetoresistive elements 20 ₁ to 20 _n (n ≧≧) provided between the first electrode 10, the second electrode 12, and the first and second electrodes. 2), and an input terminal 32 and an output terminal 34 provided on the surface of the second electrode 12 opposite to the magnetoresistive effect elements 20 ₁ to 20 _n (n ≧ 2). Each magnetoresistive element 20 _i (i = 1,..., N) is excited by magnetization vibration depending on the magnetization pinned layer 21 in which the magnetization direction is fixed, and the direction and strength of the flow of the spin injection current. The magnetization free layer 23 and the spacer layer 22 provided between the magnetization fixed layer 21 and the magnetization free layer 23 have a laminated structure in which they are laminated in this order. The magnetization pinned layer 21 is electrically connected to the first electrode 10, and the magnetization free layer 23 is electrically connected to the second electrode 12. That is, the magnetoresistive effect elements 20 ₁ to 20 _n (n ≧ 2) are connected in parallel between the first electrode 10 and the second electrode 12. Unlike the present embodiment, the magnetization free layer 23 is electrically connected to the first electrode 10, the spacer layer 22 is provided on the magnetization free layer 23, and the magnetization pinned layer 21 is provided on the spacer layer 22. It may be configured to be electrically connected to the second electrode 10. The magnetoresistive elements 20 _i (i = 1,..., N) are electrically insulated from each other by an insulating film 28 provided between the first and second electrodes 10 and 12.

In the present embodiment, the magnetoresistive effect elements 20 ₁ to 20 _n (n ≧ 2) have different cross-sectional areas of the magnetization free layer 23. Here, the cross-sectional area of the magnetization free layer 23 means the area of the surface of the magnetization free layer 23 in contact with the spacer layer 22. Therefore, the magnetoresistive effect elements 20 ₁ to 20 _n (n ≧ 2) have different resonance frequencies. The magnetoresistive effect elements 20 ₁ to 20 _n (n ≧ 2) may include magnetoresistive effect elements having the same resonance frequency, but include magnetoresistive effect elements having different resonance frequencies. Yes.

In the present embodiment configured as described above, when a high frequency signal is input from the input terminal 32, each magnetoresistive effect element 20 _i (i = 1,..., N) is included in the input high frequency signal. Absorbs signal components with the same frequency as their resonance frequency. Therefore, high frequency signal components having the same frequency as the plurality of resonance frequencies are absorbed from the input high frequency signal, and the remaining high frequency signal components are output from the output terminal 34. That is, the frequency component of the unnecessary band can be attenuated. For example, as shown in FIG. 3, the magnetoresistive effect elements 20 ₁ to 20 _n (n ≧ 2) are divided into a first magnetoresistive effect element group and a second magnetoresistive effect element group. When the magnetoresistive element group has a resonance frequency in a frequency region including the frequency f ₁ and the second magnetoresistive element group has a resonance frequency in a frequency region including the frequency f ₂ (> f ₁ ). Assume. Then, as shown in FIG. 4, the high frequency filter of the present embodiment attenuates the frequency region including the frequency f ₁ and the frequency f ₂ and passes the frequency region therebetween. In the present embodiment, a plurality of magnetoresistance effect elements 20 ₁ to 20 _n (n ≧ 2) are connected in parallel between the first electrode 10 and the second electrode 12. Therefore, it becomes a small high frequency filter. Note that the first electrode 10 may be grounded.

In the present embodiment, the magnetoresistive effect elements 20 ₁ to 20 _n (n ≧ 2) arranged on the first electrode 10 are magnetoresistive effect elements having the same cross-sectional area as shown in FIG. 20 may be arranged close to each other. Further, as shown in FIG. 5B, the magnetoresistive effect elements 20a and 20b having different cross-sectional areas may be arranged close to each other. In addition, as shown in FIG. 5C, magnetoresistive elements 20a, 20b, 20c, and 20d having different cross-sectional areas may be randomly arranged.

In the present embodiment, the magnetization fixed layer 21 and the magnetization free layer 23 may be in-plane magnetization films as shown in FIG. Here, the in-plane magnetization film means that the magnetization is substantially parallel to the film surface (upper surface). Further, the magnetization pinned layer 21 and the magnetization free layer 23 may be perpendicular magnetization films as shown in FIG. Here, the perpendicular magnetization film means that the magnetization is substantially perpendicular to the film surface (upper surface). Further, as shown in FIG. 6C, the magnetization fixed layer 21 may be a perpendicular magnetization film and the magnetization free layer 23 may be an in-plane magnetization film.

The magnetization pinned layer 21 may have a configuration in which the cross-sectional area increases in the middle from the spacer layer 22 side to the electrode side as shown in FIG. Further, as shown in FIG. 7B, the longitudinal section (cross-sectional view cut along a plane perpendicular to the film surface) may have a taper shape, or as shown in FIG. You may have. The film surface shape of the magnetoresistive effect element, that is, the film surface shape of the magnetization free layer 23 may be elliptical as shown in FIG. The magnetization free layer 23 may be any one of a circle, a rectangle, and a polygon. Moreover, it is good also as a film surface shape from which a major axis and a minor axis differ. In this case, the length (major axis) in the major axis direction is desirably 500 nm or less and 10 nm or more in order to obtain good filter characteristics.

When the magnetization pinned layer is an in-plane magnetization film, the magnetization direction of the magnetization pinned layer is pinned by the antiferromagnetic layer. This antiferromagnetic layer is provided on the opposite side to the spacer layer with respect to the magnetization pinned layer. The material of the antiferromagnetic layer includes Fe—Mn, Pt—Mn, Pt—Cr—Mn, Ni—Mn, Pd—Mn, Pd—Pt—Mn, Ir—Mn, Pt—Ir—Mn, NiO. Fe ₂ O ₃ , a magnetic semiconductor, or the like can be used.

In the present embodiment, the magnetization pinned layer 21 of the magnetoresistive effect element 20 has a laminated structure having ferromagnetic layers 21a and 21c antiferromagnetically coupled via the Ru layer 21b as shown in FIG. Also good.

The magnetization free layer and the magnetization pinned layer include, for example, a magnetic metal containing one or more elements selected from the group of Fe (iron), Co (cobalt), Ni (nickel), Mn (manganese), and Cr (chromium) It consists of. For the magnetization free layer, one or more elements selected from the group of Fe, Co, Ni, Mn, and Cr, Pt (platinum), Pd (palladium), Ir (iridium), Ru (ruthenium), An alloy formed by a combination with one or more elements selected from the group of Rh (rhodium) may be used. The magnetization free layer and the magnetization pinned layer may be formed of, for example, an amorphous alloy of a rare earth-transition metal such as TbFeCo or GdFeCo, or a Co / Pt laminated structure.

The spacer layer may be either a nonmagnetic barrier layer or a nonmagnetic metal layer. For the nonmagnetic barrier layer as the spacer layer, an insulating material as a tunnel barrier layer can be used. Specifically, Al (aluminum), Ti (titanium), Zn (zinc), Zr (zirconium), Ta (tantalum), Co (cobalt), Ni (nickel), Si (silicon), Mg (magnesium), The nonmagnetic barrier layer can be composed of an oxide, nitride or fluoride containing at least one element selected from the group of Fe (iron). In particular, the nonmagnetic barrier layer includes Al ₂ O ₃ , SiO ₂ , MgO, AlN, Ta-0, Al—Zr—O, Bi ₂ O ₃ , MgF ₂ , CaF ₂ , SrTiO ₃ , AlLaO ₃ , Al—N. —O, Si—N—O, nonmagnetic semiconductors (ZnOx, InMn, GaN, GaAs, TiOx, Zn, Te, or those doped with a transition metal) can be used.

As the spacer layer, the nonmagnetic metal layer may be any of nonmagnetic metal elements such as Cu, Ag, Au, Cr, Zn, Ga, Nb, Mo, Ru, Pd, Hf, Ta, W, Pt, Bi, or An alloy containing any one or more of these can be used.

Further, a nonmagnetic metal can be used for the first and second electrodes. In this case, as the nonmagnetic metal, any one of Au, Cu, Cr, Zn, Ga, Nb, Mo, Ru, Pd, Ag, Hf, Ta, W, Pt, Bi, Al, or these An alloy containing any one or more of them can be used. In consideration of electromagration resistance and low resistance, it is desirable to use Cu, Al, or an alloy containing them.

(Second Embodiment)
Next, the high frequency filter by 2nd Embodiment of this invention is shown in FIG. FIG. 9 is a perspective view showing the high frequency filter of the present embodiment. The high frequency filter of the present embodiment is the same as the high frequency filter of the first embodiment, where the distance between the facing of the input terminal 32 and the output terminal 34 is a / It is comprised so that it may become 10 or less.

By adopting such a configuration, the high-frequency filter of the present embodiment can be easily matched with the front-stage and rear-stage circuits.

Needless to say, this embodiment also has the same effect as the first embodiment.

Hereinafter, examples of the present invention will be described.

(First embodiment)
FIG. 10 shows the high frequency filter device of the first embodiment. The high frequency filter device of this embodiment transmits the 2 GHz band.

The high frequency filter device of this example has a configuration in which the high frequency filter 1 of the first embodiment shown in FIG. 2 and ground lines 42 and 44 are provided on both sides of the high frequency filter 1, that is, on both sides of the second electrode 12. ing. The gaps (intervals) g ₁ and g ₂ between the ground lines 42 and 44 and the high frequency filter 1 are both 2 μm. The high frequency filter 1 is a coplanar line.

The input terminal 32 and the output terminal 34 have a cross-sectional area of 100 μm × 2.5 μm in a plane parallel to the film surface, and the first and second electrodes 10 and 12 have a cross-sectional area of 623 μm in a plane parallel to the film surface. × 2.5 μm. Between the first electrode 10 and the second electrode 12, magnetoresistive elements 20 having different magnetization free layers having eight different cross-sectional areas are arranged at an interval of 100 nm. The MR ratio of each magnetoresistive element 20 is 150%. The ground lines 42 and 44 both have a cross-sectional area of 623 μm × 7 μm in a plane parallel to the film surface.

FIG. 11 shows the resonance frequency characteristics of the magnetoresistive effect element 20 having the different magnetization free layers having eight different cross-sectional areas used in the high-frequency filter device of the present embodiment configured as described above. As can be seen from FIG. 11, these magnetoresistive elements 20 have resonance frequencies in the 1.8 GHz band used for mobile phones and the 3 GHz or higher band used for UWB. Therefore, the high frequency filter device of this embodiment has the filter characteristics shown in FIG. As can be seen from FIG. 12, radio waves in the 2 GHz band are transmitted, and components in the unnecessary frequency band are absorbed and attenuated.

In the present embodiment, the ground lines 42 and 44 are provided on both sides of the second electrode 12. However, the ground line 42 is disposed above the second electrode 12 via the gap g ₁ and is also connected to the ground line. 44 may be provided with a gap g ₂ below the first electrode 10.

In the present embodiment, as shown in FIG. 13, a structure without the ground line 44 may be provided.

(Second embodiment)
FIG. 14 shows a high frequency filter device according to a second embodiment of the present invention. The high-frequency filter device of this example transmits 2 GHz band. In the high-frequency filter 1 of the first embodiment shown in FIG. 2, the cross-sectional area of the first electrode 10 is larger than the cross-sectional area of the second electrode 12. It has a larger configuration.

The cross-sectional area of the input terminal 32 and the output terminal 34 is 100 μm × 2.5 μm, and the cross-sectional area of the second electrode 12 is 623 μm × 2.5 μm. The first electrode 10 has a microstrip line structure. Between the first electrode 10 and the second electrode 12, magnetoresistive effect elements 20 having different magnetization free layers having eight different cross-sectional areas were arranged at an interval of 100 nm. Each magnetoresistive effect element 20 has a characteristic of MR 150% and has the resonance frequency characteristic shown in FIG. Then, the filter characteristics of the high-frequency filter device of the present embodiment have the same filter characteristics as shown in FIG.

(Third embodiment)
FIG. 15 shows a high frequency filter device according to a second embodiment of the present invention. The high-frequency filter device of this example transmits the 2 GHz band and the 8 GHz to 10 GHz band. The high-frequency filter 1 of the first embodiment shown in FIG. 2 and ground lines 42 and 44 on both sides of the high-frequency filter 1 are provided. It is the provided structure. The gaps g ₁ and g ₂ between the ground lines 42 and 44 and the high frequency filter 1 are both 2 μm. The high frequency filter 1 is a coplanar line.

The cross-sectional area of the input terminal 32 and the output terminal 34 is 100 μm × 6.1 μm, and the cross-sectional areas of the first and second electrodes 10 and 12 are 623 μm × 6.1 μm. Between the first electrode 10 and the second electrode 12, magnetoresistive effect elements 20 having 20 different magnetization free layers with cross-sectional areas are arranged at an interval of 100 nm. The ground lines 42 and 44 are both 623 μm × 10 μm.

FIG. 16 shows the resonance frequency characteristics of the magnetoresistive effect element 20 having 20 different magnetization free layers with different cross-sectional areas. The MR of the magnetoresistive element is 150%. The filter characteristics of the high-frequency filter device of this example are as shown in FIG. Radio waves in the 2 GHz band and the 8 GHz to 10 GHz band are transmitted, and the unnecessary frequency band components are absorbed and attenuated.

In this embodiment, as shown in FIG. 18, a structure without the ground line 44 may be used.

(Fourth embodiment)
A high frequency filter device according to a fourth embodiment of the present invention is shown in FIG. The high frequency filter device of this example transmits the 2 GHz band and the 8 GHz to 10 GHz band. In the high frequency filter 1 of the first embodiment shown in FIG. 2, the second electrode 12 of the first electrode 10 is connected to the second electrode 12. The area of the facing surface is configured to be larger than the area of the surface of the second electrode 12 facing the first electrode.

The cross-sectional area of the input terminal 32 and the output terminal 34 is 100 μm × 6.1 μm, the cross-sectional area of the second electrode 12 is 312 μm × 6.1 μm, and the first electrode 10 has a microstrip line structure. Between the first electrode 10 and the second electrode 12, magnetoresistive effect elements 20 having 20 different magnetization free layers with cross-sectional areas are arranged at an interval of 100 nm. The first electrode 10 is at ground potential. The magnetoresistive effect element 20 has the same resonance frequency characteristic as shown in FIG. Therefore, the high-frequency filter device of this embodiment also has the filter characteristics shown in FIG.

(5th Example)
A high frequency filter device according to a fifth embodiment of the present invention is shown in FIG. The high frequency filter device of this embodiment transmits 2 GHz band and 8 GHz to 10 GHz band. This embodiment has first to third electrodes 10, 12, 14, and is between the first electrode 10 and the second electrode 12, and between the second electrode 12 and the third electrode 14. A high frequency filter 1 </ b> A provided with a plurality of magnetoresistive effect elements 20 therebetween is provided. In the present embodiment, the first to third electrodes are laminated in the order of the first electrode 10, the second electrode 12, and the third electrode 14. The plurality of magnetoresistive effect elements 20 between the first electrode 10 and the second electrode 12 are electrically insulated from each other by the insulating film 28, and between the second electrode 12 and the third electrode 14. The plurality of magnetoresistive elements 20 are electrically insulated from each other by the insulating film 29. Then, ground lines 42 and 44 are provided on both sides of the high-frequency filter 1A. The gaps g ₁ and g ₂ between the ground lines 42 and 44 and the high frequency filter 1A are both 2 μm.

The cross-sectional areas of the first to third electrodes 10, 12, and 14 are 312 μm × 6.1 μm, respectively. The magnetoresistive effect element 20 provided between the first electrode 10 and the second electrode 12 and between the second electrode 12 and the third electrode 14 has 20 different free cross-sectional areas. The magnetoresistive effect element 20 having a layer is disposed at an interval of 100 nm. The first and third electrodes are at ground potential.

In this embodiment, the magnetoresistive effect element 20 having a resonance frequency characteristic shown in FIG. Therefore, the high-frequency filter device of this embodiment also has the same filter characteristics as shown in FIG. According to this embodiment, it is possible to realize a minute high frequency filter device having a size of about 0.3 mm × 0.03 mm.

(Sixth embodiment)
FIG. 21 shows a high frequency filter device according to a sixth embodiment of the present invention. The high-frequency filter device of the present example is a filter that transmits a 2 GHz band. In the high-frequency filter of the first embodiment shown in FIG. 1, the magnetoresistive elements 20 ₁ to 20 _n (n ≧ 2) are magnetized. The fixing layer 21 and the spacer layer 22 are shared.

Since the oscillation characteristic of each magnetoresistive element 20 _i (i = 1,..., N) is defined by the precession of the magnetization free layer 23 _i (i = 1,..., N), this embodiment Even in the example structure, good filter characteristics can be obtained. In addition, since the magnetization pinned layer 21 and the spacer layer 22 are shared, the pinning ability of the magnetization pinned layer 21 is enhanced, and there is an effect of more stable oscillation. As a modification of the present embodiment, a structure in which only a part of the magnetization fixed layer is shared also contributes to stable oscillation. An antiferromagnetic layer (not shown) may be provided on the surface of the magnetization pinned layer opposite to the spacer layer 22.

(terms of use)
Next, usage conditions of the high frequency filter of each embodiment and example of the present invention will be described.

In the high-frequency filters (hereinafter also simply referred to as elements) of the embodiments and examples of the present invention, it is desirable that the current value flowing through the elements be constant in order to efficiently attenuate a desired frequency. The current value here refers to the amount of current flowing through the input terminal 32 of the upper electrode (second electrode). Moreover, the alternating current mentioned later refers to the amount of alternating current when the electric power received by the antenna is passed as a current to the high frequency filter via a transmission line (which may be an electric circuit or a waveguide). As a method of adjusting the current value in order to effectively use the high-frequency filter of each embodiment and example of the present invention, a method of superimposing and flowing an alternating current to be attenuated in a state where a direct current is applied, and an alternating current And a method in which the current is amplified to a constant value. Alternatively, an alternating current may be amplified and a direct current may be superimposed on it.

(When the magnetization free layer and the magnetization pinned layer are in-plane magnetization films)
(When DC current is superimposed)
It is desirable to pass a direct current that allows the magnetization free layer of the magnetoresistive effect element to maintain precession. Although it depends on the magnetic material of the magnetization free layer, when a magnetoresistive effect element having a diameter of 50 nm to 200 nm is used, it is a guideline for a direct current of about 0.2 mA to 3 mA. For example, when CoFe is used for the magnetization free layer and the magnetization pinned layer and the film thickness is 3 nm and 10 nm, respectively, and Cu with a film thickness of 8 nm is used as the spacer layer, it is free when 0.55 mA is applied as a direct current. The magnetization of the layer continues precession.

Furthermore, by current density when passing through the magneto-resistive element is inputted to the high frequency filter of the embodiments and examples of the present invention by amplifying the alternating current so that the ^{1MA / cm 2 ~ 1000MA / cm} 2, Unnecessary frequency signals can be attenuated more effectively. As an example, when the reception at the antenna is −70 dBm, it is amplified by 40 dB and superimposed on the direct current and input to the high frequency filter.

(When DC current is not superimposed)
By current density when passing through the magneto-resistive element is inputted to the high frequency filter to amplify the alternating current so that the ^{1MA / cm 2 ~ 1000MA / cm} 2, to attenuate the signal of the unwanted frequency effectively be able to. As an example, it is conceivable to amplify a signal received by an antenna by 30 dB.

Between the upper electrode (second electrode) and the lower electrode (first electrode), pairs of lengths of major axis and minor axis are (30 nm, 30 nm), (30 nm, 100 nm), (100 nm, 200 nm), Six magnetoresistive effect elements (70 nm, 200 nm), (40 nm, 100 nm), and (300 nm, 300 nm) having an elliptical cross-sectional shape are prepared, and the magnetization of the magnetization free layer is prepared. The precession frequency was examined. A magnetic field of 100 Oe was applied in the direction of the easy axis (the major axis direction of the magnetization free layer). As a result, it was found that the characteristic shown in FIG.

Also, desired filter characteristics can be obtained by applying a DC magnetic field to the magnetoresistive effect element. A permanent magnet or a coil is used as a magnetic field applying unit that applies a DC magnetic field. The state of the precession of magnetization in the magnetization free layer of the magnetoresistive effect element changes depending on the direction and strength of the magnetic field. In the magnetoresistive effect element used in the high-frequency filter of any of the embodiments and examples of the present invention, the magnetic field may be applied in either the in-plane direction or the perpendicular direction of the magnetization free layer, but the magnetization free It is desirable to apply in the vicinity of the direction parallel to or antiparallel to the easy axis direction of the layer. In this case, a wide band can be covered by using a plurality of magnetoresistance effect elements having different cross-sectional areas.

Next, in the high-frequency filter according to any one of the embodiments and examples of the present invention, whether or not the received power is amplified for each of the cases where the cross-sectional area of the magnetoresistive effect element is changed and the direct current is applied. An experiment was conducted to investigate the operation. In this experiment, FeNi having a saturation magnetization Ms of 1000 emu / cm ³ was used as the magnetization free layer and the magnetization pinned layer of the magnetoresistive effect element. The thickness of the magnetization free layer was 3 nm, and the thickness of the magnetization pinned layer was 40 nm. Cu with a film thickness of 8 nm was used for the spacer layer. The magnetoresistance effect was 100%. The resistance value was 140Ω when the magnetization directions of the magnetization free layer and the magnetization pinned layer were parallel. The experimental results are described below.

(When direct current is not applied)
Between the first electrode and the second electrode, pairs of lengths of major axis and minor axis are (30 nm, 30 nm), (30 nm, 100 nm), (100 nm, 200 nm), (70 nm, 200 nm), ( Six magnetoresistive effect elements having a cross-sectional shape of an ellipse, which are 40 nm, 100 nm) and (300 nm, 300 nm), were arranged. When power of 1 μW (−30 dBm) was received by the antenna, AC current due to reception was passed through the high frequency filter. Here, a magnetic field of 150 Oe was applied in a direction antiparallel to the magnetization direction of the magnetization free layer. As a result, a filter characteristic for cutting noise around 2 GHz indicated by a broken line in FIG. 23 was obtained. In FIG. 23, a broken line indicates a characteristic such as a fill when no DC current is passed, and a solid line indicates a filter characteristic when a DC current is passed.

In addition, pairs of lengths of major axis and minor axis are (30 nm, 30 nm), (50 nm, 200 nm), (30 nm, 100 nm), (100 nm, 200 nm), respectively, between the first electrode and the second electrode. Six types of magnetoresistive effect elements (70 nm, 100 nm) and (40 nm, 50 nm) having an elliptical cross section were arranged. In this case, power of 1 μW (−30 dBm) was received by the antenna, and alternating current due to reception was applied. Here, a magnetic field of 100 Oe was applied in a direction parallel to the magnetization direction of the magnetization free layer. As a result, a filter characteristic for cutting noise around 5 GHz indicated by a broken line in FIG. 24 was obtained. In FIG. 24, the broken line indicates the filter characteristics when no DC current is passed, and the solid line indicates the filter characteristics when DC current is passed.

In addition, pairs of lengths of major axis and minor axis are (30 nm, 30 nm), (30 nm, 100 nm), (100 nm, 200 nm), (70 nm, 200 nm), respectively, between the first electrode and the second electrode. Six magnetoresistive effect elements (40 nm, 100 nm) and (300 nm, 300 nm) having an elliptical cross-sectional shape were arranged. When the received power at the antenna was -70 dBm, the signal intensity was amplified to 40 dB using an amplifier. When a magnetic field of 150 Oe was applied in a direction antiparallel to the magnetization direction of the magnetization free layer, a filter characteristic that cuts noise around 2 GHz was obtained. It was confirmed that the SN ratio was improved as compared with the case where the received power was not amplified.

(When direct current is applied)
The major axis and minor axis length pairs between the first electrode and the second electrode are (30 nm, 30 nm), (30 nm, 100 nm), (100 nm, 200 nm), (70 nm, 200 nm), (40 nm, respectively. , 100 nm), (300 nm, 300 nm), and six magnetoresistive elements having an elliptical cross section. When power of 1 μW (−30 dBm) was received by the antenna, an AC current was received while a DC current of 0.55 mA was passed through the high frequency filter. Here, a magnetic field of 150 Oe was applied in a direction antiparallel to the magnetization direction of the magnetization free layer. As a result, a filter characteristic for cutting noise around 2 GHz indicated by the solid line in FIG. 23 was obtained. A reduction in noise level was confirmed compared to the case where no direct current was superimposed.

In addition, a pair of lengths of major axis and minor axis between the upper electrode and the lower electrode is (30 nm, 30 nm), (50 nm, 200 nm), (30 nm, 100 nm), (100 nm, 200 nm), (70 nm, 100 nm), respectively. , (40 nm, 50 nm), which are magnetoresistive elements having an elliptical cross section. In this case, 1 μW (−30 dBm) of power was received by the antenna, and an AC current was received while a DC current of 0.55 mA was passed through the high frequency filter. Here, a magnetic field of 100 Oe was applied in a direction parallel to the magnetization direction of the magnetization free layer. As a result, a filter characteristic for cutting noise around 5 GHz indicated by a solid line in FIG. 24 was obtained. A reduction in noise level was confirmed compared to the case where no direct current was superimposed.

In addition, pairs of lengths of major axis and minor axis are (30 nm, 30 nm), (30 nm, 100 nm), (100 nm, 200 nm), (70 nm, 200 nm), respectively, between the first electrode and the second electrode. Six magnetoresistive effect elements (40 nm, 100 nm) and (300 nm, 300 nm) having an elliptical cross-sectional shape were arranged. When the received power at the antenna was -70 dBm, the signal intensity was amplified to 40 dB using an amplifier. When a magnetic field of 150 Oe was applied in a direction antiparallel to the magnetization direction of the free layer by superimposing a direct current of 0.55 mA, a filter characteristic that cuts noise around 2 GHz was obtained. It was confirmed that the SN ratio was improved as compared with the case where the received power was not amplified.

(When the magnetization free layer and the magnetization pinned layer are perpendicular magnetization films)
Next, a case where the magnetization free layer and the magnetization fixed layer are perpendicular magnetization films will be described. When the magnetization free layer and the magnetization pinned layer are perpendicular magnetization films, the magnetization directions of the magnetization free layer and the magnetization pinned layer are substantially perpendicular to the film surface. The shape of the magnetization free layer may be an ellipse or a rectangle as in the case of using the in-plane magnetization film. Moreover, it is good also as a polygon. One of the merits of using the perpendicular magnetization film is that the resonance frequency can be changed not only by the shape anisotropy but also by the magnetic anisotropy constant (Kerg / cm ³ ). By making the shape of the magnetization free layer isotropic, the magnetoresistive effect elements can be arranged more closely, and thus the area can be reduced. Furthermore, by increasing the magnetic anisotropy constant, the resonance frequency of the magnetoresistive effect element can be set to a higher frequency band. For example, when FePd having a film thickness of 3 nm is used for the magnetization free layer, the resonance frequency can be set to 20 GHz by setting K = 8Merg / cm ³ .

When the magnetization free layer and the magnetization pinned layer are perpendicular magnetization films, the cross-sectional shape is circular and the diameter is 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, and 100 nm. The precession frequency of the magnetization free layer of the magnetoresistive effect element was investigated. A 300 Oe magnetic field was applied in the direction of the easy axis of the magnetization free layer. As a result, the characteristics shown in FIG. 25 were obtained.

(When no magnetic field is applied)
In addition, the cross-sectional shape is circular between the first electrode and the second electrode, and the diameter is 32 nm, 34 nm, 38 nm, 40 nm, 42 nm, 46 nm, 52 nm, 58 nm, 73 nm, 76 nm, 82 nm, 94 nm, 100 nm, 132 nm. A high-frequency filter according to any one of the first to second embodiments and examples of the present invention in which 16 magnetoresistive effect elements of 150 nm and 200 nm are arranged was produced. As the magnetization free layer, FePd having a film thickness of 3 nm was used, the saturation magnetization Ms was 1000 emu / cm ³ , and the anisotropy constant K was 6 Merg / cm ³ . The spacer layer was made of MgO having a thickness of 1 nm, and the magnetic pinned layer was made of FePd having a thickness of 8 nm. The filter characteristics when direct current was applied to this high frequency filter and when it was not supplied were examined.

(When direct current is not applied)
A signal that received 1 μW of power with the antenna was input to the high-frequency filter. As a result, a filter characteristic that transmits only 5 GHz between 1.5 GHz and 9 GHz as indicated by a broken line in FIG. 26 was obtained. Note that the filter characteristic indicated by the solid line in FIG. 26 indicates a case where a direct current is applied. When the received power at the antenna was −60 dBm, it was amplified by 30 dB using an amplifier and input to the high frequency filter. As a result, only 5 GHz was transmitted between 1.5 GHz and 9 GHz. It was confirmed that the SN ratio was improved as compared with the case where the received power was not amplified.

(When direct current is applied)
A direct current of 0.55 mA was superimposed on the signal that received 1 μW of power from the antenna and input to the high-frequency filter. As a result, a filter characteristic that transmits only 5 GHz between 1.5 GHz and 9 GHz, which is indicated by a solid line in FIG. 26, was obtained. A reduction in noise level was confirmed compared to the case where no direct current was superimposed.

Also, when the received power at the antenna was −60 dBm, it was amplified by 30 dB using an amplifier and input to the high frequency filter. As a result, only 5 GHz was transmitted between 1.5 GHz and 9 GHz. It was confirmed that the SN ratio was improved as compared with the case where the received power was not amplified.

(When applying a magnetic field)
Next, a case where a DC magnetic field is further applied to the magnetoresistive effect element will be described. As a method for applying a DC magnetic field, there are a method using a permanent magnet and a method using a coil. The characteristics of precession of the magnetization free layer of the magnetoresistive effect element change depending on the direction and strength of the magnetic field. In the magnetoresistive effect element used in the high frequency filter of any of the embodiments and examples of the present invention, the magnetic field can be applied in either the direction parallel to the film surface of the magnetization free layer or the direction perpendicular to the film surface. Although it is good, it is desirable to apply in the vicinity of a direction parallel to or antiparallel to the easy axis of magnetization of the magnetization free layer. Below, each of the case where a direct current is supplied and the case where it does not supply are demonstrated.

(When direct current is not applied)
FePd having a saturation magnetization Ms of 100 emu / cm ³ was used as the magnetization free layer and the magnetization pinned layer. MgO was used as the spacer layer. The film thicknesses of the magnetization free layer, the spacer layer, and the magnetization pinned layer were 3 nm, 1 nm, and 8 nm, respectively.
Between the first electrode and the second electrode, there are 10 types of magnetoresistive effect elements having a circular cross section and a diameter of 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm. An arranged high frequency filter was created. A magnetic field of 300 Oe was applied in a direction parallel to the magnetization of the magnetization free layer. A signal that received 1 μW of power with the antenna was input to the high-frequency filter. As a result, it was confirmed that a filter characteristic that transmits only 20 GHz in a band of 17 GHz to 24 GHz indicated by a broken line in FIG. 27 can be obtained. In FIG. 27, the filter characteristics indicated by the solid line are those when a direct current is applied.

Subsequently, when the received power at the antenna was −60 dBm, the signal was amplified by 30 dB and input to the high frequency filter. It was confirmed that the S / N ratio was improved compared to the case where the signal was not amplified, and only 20 GHz was transmitted in the 17 GHz-24 GHz band.

(When direct current is applied)
A high-frequency filter is used when no direct current is applied. When 1 μW of power was received by the antenna, a 0.8 mA direct current was superimposed and input to the high frequency filter. As a result, a filter characteristic that effectively transmits only a 20 GHz signal in a band of 17 GHz to 24 GHz indicated by a solid line in FIG. 27 was confirmed. A reduction in noise level was confirmed compared to the case where no direct current was superimposed.

Next, when the received power at the antenna was −60 dBm, the signal was amplified by 30 dB and a direct current of 0.8 mA was superimposed and input to the high frequency filter. It was confirmed that the S / N ratio was improved compared to the case where the signal was not amplified, and only 20 GHz was transmitted in the 17 GHz-24 GHz band.

(When the magnetization free layer is an in-plane magnetization film and the magnetization pinned layer is a perpendicular magnetization film)
The magnetization direction of the magnetization free layer is set substantially parallel to the film surface, and the magnetization direction of the magnetization fixed layer is set substantially perpendicular to the film surface. The magnetization direction of the magnetization free layer may be a direction substantially perpendicular to the film surface, and the magnetization direction of the magnetization pinned layer may be a direction substantially parallel to the film surface. In that case, it is desirable to make the film thickness sufficient so that the magnetization of the magnetization pinned layer does not fluctuate when a current is applied. For example, when the thickness of the magnetization free layer is 3 nm, the magnetization direction of the magnetization fixed layer is not fluctuated by the current by setting the thickness of the magnetization fixed layer to 40 nm.

The magnetization free layer is an in-plane magnetization film, the magnetization pinned layer is a perpendicular magnetization film, and the cross-sectional shape is circular and the diameters are 113 nm, 117 nm, 122 nm, 127 nm, 141 nm, 149 nm, 160 nm, 172 nm, 189 nm, 211 nm, and 244 nm. The precession frequency of the magnetization free layer was examined for a certain 11 types of magnetoresistive effect elements. As a result, the characteristics shown in FIG. 28 were confirmed.

(When applying a magnetic field)
A DC magnetic field is applied to the magnetoresistive element. As a method for applying a DC magnetic field, there are a method using a permanent magnet and a method using a coil. The characteristics of precession of the magnetization free layer of the magnetoresistive effect element change depending on the direction and strength of the magnetic field. In each embodiment or example of the present invention, the magnetic field direction may be applied to either the direction parallel to the film surface of the magnetization free layer or the direction perpendicular to the film surface. It is desirable to apply a magnetic field in a direction parallel or antiparallel to the magnetization of the pinned layer. Below, each of the case where a direct current is supplied and the case where it does not supply are demonstrated.

(When direct current is not applied)
A high frequency in which eight types of magnetoresistive effect elements having a circular cross-sectional shape and a diameter of 57 nm, 58 nm, 62 nm, 67 nm, 74 nm, 80 nm, 90 nm, and 97 nm are disposed between the first electrode and the second electrode Created a filter. When a magnetic field of 100 Oe was applied in a direction perpendicular to the film surface of the magnetization free layer (parallel to the magnetization of the magnetization pinned layer) and 1 μW of power was received by the antenna, an AC current from the reception was passed through the high frequency filter. As a result, a filter characteristic that transmits only 2 GHz in the band of 1 GHz to 3 GHz indicated by a broken line in FIG. 29 was confirmed. Note that the filter characteristic indicated by the solid line in FIG. 29 is a characteristic when a direct current is applied.

Next, when the received power at the antenna is −60 dBm, the signal is amplified by 30 dB and input to the high frequency filter. A magnetic field of 100 Oe was applied in a direction perpendicular to the film surface of the magnetization free layer (parallel to the magnetization of the magnetization pinned layer). It was confirmed that the S / N ratio was improved as compared with the case where the signal was not amplified, and only 2 GHz was transmitted in the band of 1 GHz to 3 GHz.

(When direct current is applied)
A signal that receives 1 μW of power from the antenna while applying a 100 Oe magnetic field in a direction perpendicular to the film surface of the magnetization free layer of the high-frequency filter in which no direct current is passed (parallel to the magnetization of the magnetization pinned layer) is 0 A direct current of .55 mA was passed through the high frequency filter. As shown by the solid line in FIG. 29, more effective filter characteristics were obtained when a direct current was passed compared to when no direct current was passed. That is, a reduction in the noise level was confirmed as compared with the case where no direct current was superimposed.

Next, when the received power at the antenna was −60 dBm, the signal was amplified by 30 dB and a DC current of 0.55 mA was superimposed and input to the high frequency filter. A magnetic field of 100 Oe was applied in a direction perpendicular to the film surface of the magnetization free layer (parallel to the magnetization of the magnetization pinned layer). It was confirmed that the S / N ratio was improved as compared with the case where the signal was not amplified, and only 2 GHz was transmitted in the band of 1 GHz to 3 GHz.

(When no magnetic field is applied)
(When direct current is not applied)
Eleven magnetoresistances having a circular cross-section and a diameter of 113 nm, 117 nm, 122 nm, 127 nm, 141 nm, 149 nm, 160 nm, 172 nm, 189 nm, 211 nm, and 244 nm between the first electrode and the second electrode A high frequency filter in which an effect element is arranged was created. As the magnetization free layer, FeNi having a film thickness of 2.5 nm and a saturation magnetization Ms of 1000 emu / cm ³ was used. Cu having a thickness of 8 nm was used as the spacer layer, and FePd having a thickness of 8 nm, Ku of 8 Merg / cm ³ , and Ms of 1000 emu / cm ³ was used as the spacer layer. A signal that received 1 μW of power with the antenna was input to the high-frequency filter. As a result, a filter characteristic that transmits only 5 GHz in the band of 1.5 GHz to 7 GHz indicated by a broken line in FIG. 30 was confirmed.

Next, when the received power at the antenna was −60 dBm, the signal was amplified by 30 dB and input to the high frequency filter. It was confirmed that the S / N ratio was improved as compared with the case where the signal was not amplified, and only 5 GHz was transmitted in the band of 1.5 GHz to 7 GHz.

(When direct current is applied)
The high frequency filter used when no direct current is applied is used. In this case, when 1 μW of electric power was received by the antenna, an alternating current flowing by reception was input to the high-frequency filter while a direct current of 0.55 mA was passed. As a result, a filter characteristic that transmits only 5 GHz in a band of 1.5 GHz to 7 GHz indicated by a solid line in FIG. 30 was confirmed.

Next, when the received power at the antenna was −60 dBm, the signal was amplified by 30 dB and a DC current of 0.55 mA was superimposed and input to the high frequency filter. It was confirmed that the S / N ratio was improved as compared with the case where the signal was not amplified, and only 5 GHz was transmitted in the band of 1.5 GHz to 7 GHz.

Next, the relationship between wavelength and electrode size will be described.

In the propagation of high-frequency signals, there is a problem that the loss increases as the wavelength of the signal to be transmitted approaches the transmission line (propagation path, electrode length). In order to improve this, there are a method of designing the electrode length short and a method of arranging an electrode functioning as a ground line in the vicinity of the signal line.

(Guidelines for designing a short electrode length)
Assuming use in a band up to 40 GHz, the wavelength a of radio waves of 40 GHz in vacuum is 7.5 mm. For simplicity, the effects of wavelength shortening will be omitted and discussed. The high frequency characteristics were calculated when the electrode length (distance between the opposite surface of the input terminal and the output terminal and the surface on the opposite side) was a / 10 (0.75 mm). In this calculation model, as shown in FIG. 31A, an electrode 52 made of Cu is formed on an SiO ₂ film 50, and an input terminal 54 and an output terminal 56 are provided on the electrode 52. The width of this model was 5 μm. The calculation result is shown in FIG. 31A and 31B, reference numeral S11 indicates a reflection characteristic of the input terminal 54, and reference numeral S21 indicates a transmission characteristic from the input terminal 54 to the output terminal 56 through the electrode 52.

As can be seen from FIG. 31B, in the band up to 40 GHz, the transmission characteristic S21 is −3 dB or more. Note that −3 dB means that half of the input power is transmitted. From this, it was found that by designing the size of “electrode length a / 10 or less”, the transmission amount can be −3 dB or more in a band of 40 GHz or less, and a space-saving structure can be achieved. .

In the high-frequency filter according to the embodiment of the present invention, by designing the width direction wide and designing the length direction short, a space-saving structure and greater transmission characteristics can be obtained. As shown in FIG. 32A, the model size was changed so that the electrode length was 250 μm and the horizontal width was 15 μm so that the occupied area would be the same as the case where the electrode length was 750 μm and the horizontal width was 5 μm. The calculation result in this case is shown in FIG. As can be seen from FIG. 32 (b), the transmittance at 40 GHz was improved to -0.11 dB or more (98% or more). Since an important point for obtaining the filter function of one embodiment of the present invention is to dispose the magnetoresistive effect element, the layout of the magnetoresistive effect element is not affected unless the occupied area changes. In addition, there is an advantage that high-frequency propagation characteristics (corresponding to loss of input signal) can be improved.

As described above, the loss can be reduced to 3 dB or less by setting the electrode length to a / 10 or less.

Next, a method for arranging a ground line or an electrode functioning as a ground plane in the vicinity of the signal line will be described.

As a method for improving the amount of signal transmission, it is known that a ground line for converging an electric field generated from a signal line or a ground plane close to each other reduces reflection of an input signal and increases a transmission component. In the high frequency filter of one embodiment of the present invention, a ground line or an electrode functioning as a ground plane may be disposed in the vicinity of the signal line.

As a structure in which the ground line is arranged in parallel with the signal line, for example, there is a coplanar structure as shown in FIG. In the coplanar structure shown in FIG. 10, it was examined how the signal transmission amount changes depending on the gap interval between the signal line and the ground line. The result is shown in FIG. In this case, the electrode length is 750 μm.

As can be seen from FIG. 33, the transmission amount can be 80% or more by setting the gap between the signal line and the ground line to 3 μm or less. In order to efficiently converge the lines of electric force generated from the signal line to the ground line, assuming that the line width of the signal line is w, the line width of the ground line is b, and the gap between the signal line and the ground line is g,
g ≦ b-2w
It is desirable to design to satisfy the following conditions. In this case, the transmission amount can be about 80% or more.

Other methods of placing a ground line or ground plane near the signal line include a microstrip line structure in which a signal line is placed on the ground plane via a dielectric, or a dielectric surrounded by a ground plane. There is a stripline structure in which signal lines are arranged.

Next, an application of a high frequency filter according to an embodiment of the present invention will be described.

Even if the method of applying a magnetic field to the magnetoresistive element is a method using a permanent magnet 70 as shown in FIGS. 34 (a) and 34 (b) and FIGS. 35 (a) and 35 (b), As shown in FIG. 36, a method using a coil 80 used in a hard disk may be used. In any case, “parallel direction”, “direction orthogonal to the film surface”, or “direction orthogonal to the direction orthogonal to the film surface” with respect to the magnetization direction of the magnetization free layer of the magnetoresistive effect element 20 A magnetic field may be applied to the. 34 (a) and 34 (b), a high frequency filter 1 according to an embodiment of the present invention is provided on an insulating substrate (for example, a sapphire substrate) 60. The permanent magnet 70 is provided above. In the first example, the high frequency filter 1 is covered with the upper lid 62 and packaged. In the first example, the permanent magnet 70 is provided above the high-frequency filter 1, but may be provided below.

In the second example shown in FIGS. 35A and 35B, the high-frequency filter 1 according to the embodiment of the present invention is provided on an insulating substrate (for example, a sapphire substrate) 60, and this high-frequency filter is provided. 1 has a configuration in which permanent magnets 70a and 70b are provided on a pair of opposing side surfaces. And also in this 2nd example, the high frequency filter 1 is covered with the upper cover 62, and is packaged. The third example shown in FIG. 36 has a configuration in which a pair of coils 80a and 80b are provided on the side surface of the high-frequency filter in one embodiment of the present invention.

Hereinafter, an example using a permanent magnet will be described, but a coil may be used instead of the permanent magnet.

In the magnetoresistive element used in the high frequency filter according to the embodiment of the present invention, the magnetization free layer has magnetization substantially parallel to the film surface, and the magnetization fixed layer has magnetization substantially perpendicular to the film surface. In this embodiment, an example in which no magnetic field is applied and no direct current is superimposed is shown in FIG. An example in which a direct current is applied without applying a magnetic field is shown in FIG. Noise level was improved by superimposing DC current.

Next, in FIGS. 37 (a) and 37 (b), examples using amplifiers for amplifying signals input to the input terminals are shown in FIGS. 38 (a) and 38 (b), respectively. Also in this example, the noise level was improved by superimposing the direct current.

Next, an example of applying a magnetic field using a permanent magnet will be described. A coil may be used instead of the permanent magnet. In the magnetoresistive effect element used in this example, when the magnetization free layer and the magnetization fixed layer have magnetization substantially parallel to the film surface, the magnetization free layer and the magnetization fixed layer have magnetization substantially perpendicular to the film surface. Or one of the magnetization free layer and the magnetization pinned layer may have magnetization substantially parallel to the film surface and the other may have magnetization substantially perpendicular to the film surface.

An example in which no direct current is superimposed is shown in FIG. An example in which direct current is applied is shown in FIG. Noise level was improved by superimposing DC current.

Next, an example using an amplifier for amplifying an input signal will be described. An example in which no direct current is superimposed is shown in FIG. It was confirmed that the SN ratio was improved by amplifying the alternating current. An example in which a direct current is applied is shown in FIG. Noise level was improved by superimposing DC current. In the example shown in FIGS. 40A and 40B, the amplifier is provided in the previous stage of the high-frequency filter, but may be provided in the subsequent stage.

Further, in the above example, the permanent magnet is provided in parallel to the pair of opposing side surfaces of the high-frequency filter, but in FIGS. 41 (a), 41 (b), FIGS. As shown, it may be arranged above or below the high frequency filter. FIG. 41A shows an example in the case where the direct current is not superimposed, and FIG. 41B shows an example in the case where the direct current is superimposed. 42 (a) and 42 (b) show examples in which signals are amplified using amplifiers in FIGS. 41 (a) and 41 (b), respectively. In addition, you may arrange | position a permanent magnet in both the upper direction and the downward direction of a high frequency filter.

Next, FIG. 43 shows a circuit of a transmission / reception system in the microwave band using the high-frequency filter of one embodiment of the present invention. The transmission / reception system includes a reception unit and a transmission unit, and the high-frequency filters 100A and 100B according to the embodiment of the present invention are used for the transmission unit and the reception unit, respectively.

The signal received by the antenna is input to the high frequency filter 1 of the receiving unit via the switch. The output of the high frequency filter 100A is mixed with the signal of the local oscillator in the mixer of the receiving unit, and sent to the intermediate frequency bandpass filter (IFBPF) of the receiving unit. The output of this IFBPF is sent to the baseband. A signal transmitted from the baseband is sent to the IFBPF of the transmission unit. The output of IFBPF is mixed with the signal of the local oscillator in the mixer of the transmission unit and sent to the high frequency filter 100B of the transmission unit. The output of the high frequency filter 100B is amplified by a transmission amplifier and then sent to an antenna via a switch for transmission.

Here, the high frequency filters 100A and 100B may include an amplifier for amplification and a power supply for direct current application. By setting it as such a transmission / reception system, the unnecessary frequency component contained in a received signal can be removed. Also, unnecessary frequency components included in the transmission signal can be removed when transmitting. In this transmission / reception system, an amplification amplifier may be provided after the high frequency filters 100A and 100B.

Next, MIMO (Multiple Input Multiple Multiple Output) using a plurality of antennas for transmission and reception will be described. In this MIMO, there is a problem that radio waves are received by an adjacent antenna during transmission, and a means for attenuating unnecessary signals has been desired. FIG. 44 shows a circuit diagram of a MIMO transmission / reception system using the high frequency filter according to the embodiment of the present invention. With the configuration as shown in FIG. 44, it is possible to attenuate unnecessary signals that leak to the receiving side during transmission.

Next, as shown in FIGS. 45 (a) and 45 (b) and FIGS. 46 (a) and 46 (b), by using a coil and a capacitor, the subsequent stage of the high-frequency filter 1 according to the embodiment of the present invention. It is possible to prevent unnecessary DC current from flowing. In this case, since direct current cannot pass through the capacitor, it flows to the coil side. 45A shows an example in which a direct current is superimposed without applying a magnetic field to the high-frequency filter 1, and FIG. 45B amplifies the signal with an amplifier in the example shown in FIG. 45A. An example of the case is shown. 46A shows an example in which a magnetic field is applied to the high-frequency filter 1 and a direct current is superimposed, and FIG. 46B shows a case in which the signal is amplified by an amplifier in the example shown in FIG. 46A. An example of

1 high frequency filter 10 first electrode 12 second electrode 20 magneto-resistive element ₂₀ 1 ~ 20 _n magnetoresistive element 21 pinned layer 22 a spacer layer 23 magnetization free layer 28 insulating film 32 input terminal 34 output terminal

Claims (9)

1. A first electrode;
   A second electrode provided on the first electrode;
   A magnetization pinned layer provided between the first electrode and the second electrode, the magnetization direction of which is fixed, and a magnetization free layer which is excited by magnetization vibration in accordance with a direction and intensity of flow of a spin injection current And a plurality of magnetoresistive elements each having a different cross-sectional area of the magnetization free layer, and a spacer layer provided between the magnetization pinned layer and the magnetization free layer,
   An input terminal for inputting a signal and an output terminal for outputting a signal, which are provided apart from each other on the second electrode;
   An element for high frequency, comprising:
2. The high-frequency element according to claim 1, further comprising a magnetic field applying unit that applies a magnetic field to the magnetoresistive effect element.
3. The high frequency device according to claim 1, wherein the input terminal is connected to a direct current source.
4. The high frequency device according to claim 1, wherein an amplifier is connected to one of the input terminal and the output terminal.
5. 2. The distance between the opposite surfaces of the input terminal and the output terminal is a / 10 or less, where a is the shortest wavelength of the input signal. High frequency element.
6. A grounding electrode that is grounded and disposed at an interval with respect to at least one of the pair of opposing side surfaces of the second electrode parallel to the direction from the input terminal to the output terminal. The high-frequency device according to claim 1, wherein
7. When the width of the second electrode is w, the width of the ground electrode is b, and the distance of the gap is g,
   g ≦ b-2w
   The high frequency device according to claim 6, wherein the relationship is satisfied.
8. The high-frequency element according to claim 1, wherein the first electrode has a larger area of the facing surface than the second electrode.
9. A first electrode;
   A second electrode provided on the first electrode;
   A third electrode provided on the second electrode;
   A magnetization pinned layer provided between the first electrode and the second electrode, the magnetization direction of which is fixed, and a magnetization free layer which is excited by magnetization vibration in accordance with a direction and intensity of flow of a spin injection current And a first magnetoresistive element group having a spacer layer provided between the magnetization pinned layer and the magnetization free layer, each having a different cross-sectional area of the magnetization free layer; ,
   A magnetization pinned layer provided between the second electrode and the third electrode, the magnetization direction of which is fixed, and a magnetization free layer which is excited by magnetization vibration in accordance with the direction and strength of flow of the spin injection current And a second magnetoresistive element group having a spacer layer provided between the magnetization pinned layer and the magnetization free layer, each having a different cross-sectional area of the magnetization free layer; ,
   An element for high frequency, comprising:

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