JP6617402B2 - Detector - Google Patents

Description

  The present invention relates to a detector applied to non-wired signal transmission, communication functional elements, and the like.

  In recent years, in a receiving apparatus of a wireless communication system, miniaturization and low power consumption have been demanded, and many functions have been integrated into an IC. On the other hand, the increase in the sensitivity of reception is rapidly progressing, and the increase in the sensitivity of the detection circuit is one of the important issues in configuring the receiver. For example, Patent Document 1 proposes an FSK detector having a phase comparator, a low-pass filter, an amplifier, a CCO (Current Controlled Oscillator), and an FSK detector current source.

  In recent years, the field of spintronics, which uses the charge and spin of electrons simultaneously, has attracted much attention compared to the field of electronics that applies the charge of electrons, and the spin torque diode effect that rectifies high-frequency signals to DC voltage is known. (See Non-Patent Document 1).

JP2009-212901

Nature, Vol. 438, no. 7066, pages 339-342 (2005)

  The FSK detector described in Patent Document 1 includes a phase comparator, a low-pass filter, an amplifier, a CCO (Current Controlled Oscillator), and an FSK detector current source. As an example, the phase comparator includes a flip-flop circuit and a NAND circuit. As an example, the low-pass filter includes a capacitor connected in parallel to the input signal and a resistor connected in series to the input signal. The gain of the amplifier is controlled by a current from a control block having a reference power source, an external resistor, a transistor, a constant current source, and an external adjustment terminal. As an example, the CCO includes a resistor, a capacitor, an inductor, and a transistor. Therefore, the FSK detector described in Patent Document 1 has a problem that the circuit configuration becomes complicated. In this case, problems such as an increase in manufacturing cost and a decrease in yield cannot be avoided.

  In order to solve the above problems, a detector according to the present invention includes a magnetoresistive effect element including a magnetization fixed layer and a magnetization free layer disposed via a spacer layer, and the magnetoresistive effect element in the stacking direction. A pair of electrodes disposed via a magnetoresistive effect element; a magnetic field applying mechanism for applying a magnetic field to the magnetoresistive effect element; the magnetoresistive effect element having at least a first frequency component; and the first An input terminal for supplying a frequency modulation signal including a second frequency component different from the frequency of the output, an output terminal for extracting an output voltage from the magnetoresistive element, and a detection unit for detecting the output voltage, The pair of electrodes are electrically connected to the input terminal and the output terminal, and the magnetic field application mechanism includes a first output voltage as the output voltage corresponding to the first frequency and the second frequency. Vs. The magnetic field having a magnitude such that there is a voltage difference from the second output voltage as the output voltage is applied, and the detection unit detects the frequency modulation signal based on the output voltage. To do.

  According to the detector of the present invention having the above characteristics, the spin torque diode effect of the magnetoresistive effect element can be expressed. Further, the magnetic field applying mechanism applies a magnetic field having a magnitude such that there is a voltage difference between the first output voltage corresponding to the first frequency and the second output voltage corresponding to the second frequency. By applying to, it is possible to distinguish and detect the first frequency component and the second frequency component of the frequency modulation signal using the voltage difference. Therefore, the frequency modulation signal can be detected with a relatively simple circuit configuration including the magnetoresistive effect element.

  Furthermore, in the detector according to the present invention, the magnetic field application mechanism is configured so that the ferromagnetic resonance frequency of the magnetization of the magnetization free layer coincides with one of the first frequency and the second frequency. A magnetic field is applied.

According to the detector of the present invention having the above characteristics, the ferromagnetism of the magnetization of the magnetization free layer depending on the magnitude of the magnetic field applied to the magnetoresistive effect element, either the first frequency or the second frequency. Since the resonance frequency can be the same, either the first output voltage or the second output voltage can be increased. Therefore, the voltage difference between the first output voltage and the second output voltage can be increased.

  Furthermore, the detector of the present invention is characterized in that the magnetic field application mechanism variably controls the magnetic field applied to the magnetoresistive effect element.

  According to the detector of the present invention having the above characteristics, it is possible to tuneably control the frequency characteristics of the spin torque diode effect of the magnetoresistive effect element. Therefore, even if the first frequency and the second frequency of the frequency modulation signal change to some extent, the first frequency component and the second frequency component of the frequency modulation signal can be distinguished and detected.

  Furthermore, the detector of the present invention has a bias current application mechanism for applying a bias current to the magnetoresistive effect element.

  According to the detector of the present invention having the above characteristics, the spin transfer torque acting on the magnetization of the magnetization free layer can be increased, and the sensitivity of the spin torque diode can be increased. Therefore, the voltage difference corresponding to the frequency difference between the first frequency and the second frequency of the frequency modulation signal can be increased.

  Furthermore, the detector of the present invention is characterized in that the bias current is applied in a direction from the magnetization free layer to the magnetization fixed layer.

  According to the detector of the present invention having the above characteristics, since electrons flow from the magnetization fixed layer to the magnetization free layer, the spin transfer torque acting on the magnetization of the magnetization free layer can be exerted more and the spin torque diode sensitivity can be further increased. It becomes possible to enlarge. Therefore, the voltage difference between the first output voltage and the second output voltage can be further increased.

  Furthermore, the detector of the present invention is characterized in that 0.4 nm <t1 <t2 is satisfied, where t1 is the thickness of the magnetization free layer and t2 is the thickness of the magnetization fixed layer.

According to the detector of the present invention having the above characteristics, by setting t1 <t2, the spin transfer torque works efficiently on the magnetization of the magnetization free layer, and the spin torque diode effect can be efficiently expressed. . Further, by setting 0.4 nm <t1, saturation magnetization reduction of the magnetization free layer can be prevented, and the spin torque diode effect can be efficiently expressed. Therefore, the voltage difference between the first output voltage and the second output voltage can be increased.

  According to the present invention, it is possible to simplify the circuit of a detector applied to non-wired signal transmission, a communication functional element, and the like.

1 is a schematic diagram of a detector 100 according to a first embodiment of the present invention. It is a figure which shows the frequency characteristic of a spin torque diode effect. It is sectional drawing of the magnetoresistive effect element 3 of FIG. It is a figure which shows the relationship between the output voltage and frequency in the 1st Embodiment of this invention. It is a figure which shows the relationship between the output voltage and frequency in the 1st Embodiment of this invention. It is a figure which shows the relationship between a bias current and a spin torque diode sensitivity. It is a figure which shows the time waveform of a frequency modulation signal. It is a figure which shows the time dependence of an output voltage. It is the schematic of the detector 102 which concerns on the 2nd Embodiment of this invention. It is a figure which shows the relationship between the output voltage and frequency in the 3rd Embodiment of this invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings. However, the present invention is not limited by the contents described in the following embodiments. Furthermore, the present embodiment can be added, omitted, replaced, and otherwise changed without departing from the spirit of the present embodiment.

(First embodiment)
FIG. 1 is a schematic diagram of a detector 100 according to the first embodiment of the present invention. The detector 100 includes an input terminal 1, a lower electrode 2, a magnetoresistive effect element 3, an upper electrode 4, a magnetic field application mechanism 5, a bias current application mechanism 6, an output terminal 7, and a detection unit 8.

The input terminal 1 is electrically connected to the upper electrode 4 and supplies the magnetoresistive effect element 3 with a frequency modulation signal including at least a first frequency component and a second frequency component different from the first frequency. It has the function to do. Hereinafter, the first frequency may be expressed as f1, and the second frequency may be expressed as f2. The detector 100 includes a ground terminal 12, and the ground terminal 12 is connected to the ground and functions as a reference potential of the input terminal 1.

The output terminal 7 is electrically connected to the upper electrode 4 and takes out a first output voltage corresponding to the first frequency generated in the magnetoresistive effect element 3 and a second output voltage corresponding to the second frequency. It has a function. The detector 100 includes a ground terminal 72, and the ground terminal 72 is connected to the ground and functions as a reference potential for the output terminal 7.

The detection unit 8 has a function of detecting an output voltage taken out from the output terminal 7. If there is a voltage difference (hereinafter also referred to as ΔV) between the first output voltage and the second output voltage, the first frequency component and the second frequency component of the frequency modulation signal can be distinguished and detected. It becomes possible.

The lower electrode 2 and the upper electrode 4 serve as a pair of electrodes, and are disposed via the magnetoresistive effect element 3 in the stacking direction of the magnetoresistive effect element 3. That is, the direction of the current with respect to the magnetoresistive effect element 3 in the direction intersecting the surface of each layer constituting the magnetoresistive effect element 3, for example, the direction perpendicular to the surface of each layer constituting the magnetoresistive effect element 3 It functions as a pair of electrodes for flowing in the direction). The lower electrode 2 is connected to the ground. The lower electrode 2 is electrically connected to the input terminal 1 and the output terminal 7 via the magnetoresistive effect element 3.

The lower electrode 2 and the upper electrode 4 are preferably made of a high conductivity material such as Cu, Au, AuCu. Moreover, it is preferable to prescribe | regulate the planar view shape of the lower electrode 2 and the upper electrode 4 in a microstrip line type or a coplanar wave guide type. As a result, transmission loss of the frequency modulation signal can be reduced.

The magnetoresistive effect element 3 converts the frequency modulation signal input from the input terminal 1 into a first output voltage corresponding to the first frequency and a second output voltage corresponding to the second frequency by the spin torque diode effect. It has the function to convert to. The magnetoresistive effect element 3 includes a magnetization fixed layer 31, a spacer layer 32, and a magnetization free layer 33, and the magnetization fixed layer 31 and the magnetization free layer 33 are disposed via the spacer layer 32. In addition, the magnetoresistive effect element 3 is processed by a known photolithography method and etching method so that the shape in plan view becomes a circular shape, an elliptical shape, a square shape, a rectangular shape, or the like. Furthermore, when the shape in plan view is a circle, the diameter is used. When the shape is elliptical, at least the short axis of the short axis and the long axis. At least the short side of the sides is preferably 100 nm or less. Thereby, the magnetic domain of the magnetization free layer 33 can be changed to a single domain, and the spin torque diode effect can be effectively expressed.

Here, the spin torque diode effect will be described.

When a high frequency signal is input to the magnetoresistive element 3, a DC voltage (hereinafter referred to as an output voltage) proportional to the square of the amplitude of the signal is generated. This rectifying action is the spin torque diode effect. FIG. 2 is a diagram illustrating frequency characteristics of the spin torque diode effect. The horizontal axis represents the frequency of the high frequency signal, and the vertical axis represents the output voltage. As can be seen from FIG. 2, when the frequency component of the high-frequency current matches the ferromagnetic resonance frequency of magnetization of the magnetization free layer 33 (hereinafter also referred to as f0), a large output voltage is generated. This action is called spin torque ferromagnetic resonance, and the output voltage increases in proportion to the magnetoresistance change rate of the magnetoresistive element 3. The ratio of the output voltage to the power of the input high frequency signal is called spin torque diode sensitivity.

ここで、γは磁気ジャイロ定数、Ｍｓは磁化自由層３３の飽和磁化、Ｈｋは磁化自由層３３の異方性磁界、Ｈｅｘｔは磁化自由層３３に印加される外部磁界である。 Here, the ferromagnetic resonance frequency f0 will be described. f0 can be expressed as the following formula (1).

Here, γ is a magnetic gyro constant, Ms is a saturation magnetization of the magnetization free layer 33, Hk is an anisotropic magnetic field of the magnetization free layer 33, and Hext is an external magnetic field applied to the magnetization free layer 33.

Next, the magnetization fixed layer 31, the spacer layer 32, and the magnetization free layer 33 will be described.

The magnetization fixed layer 31 has a function in which the magnetization direction is not changed by a magnetic field generated from the magnetic field application mechanism 5. The magnetization fixed layer 31 is preferably composed of a high spin polarizability material such as Fe, Co, Ni, FeCo, CoFeB. Thereby, a high magnetoresistance change rate can be obtained. The thickness of the magnetization fixed layer 31 is preferably 1 nm to 10 nm. If the film thickness is too thin, the magnetoresistance change rate tends to decrease. If the film thickness is too thick, the magnetization direction of the magnetization fixed layer 31 is likely to change due to the magnetic field generated from the magnetic field application mechanism 5. Although not shown, an antiferromagnetic layer made of a material such as PtMn, FeMn, or IrMn may be inserted between the fixed magnetization layer 31 and the lower electrode 2. As a result, the fixed strength in the magnetization direction of the magnetization fixed layer 31 can be increased.

The spacer layer 32 has a function of obtaining a magnetoresistance effect by causing the magnetization of the magnetization fixed layer 31 and the magnetization of the magnetization free layer 33 to interact with each other. The spacer layer 32 may be made of a nonmagnetic conductive material such as Cu or Ag, or may be made of a nonmagnetic insulating material such as AlOx (aluminum oxide), MgO (magnesium oxide), or MgAl2O4. When the spacer layer 32 is made of a conductive material, the magnetoresistive effect element 3 exhibits a giant magnetoresistance (GMR) effect. When the spacer layer 32 is made of an insulating material, the magnetoresistive effect element 3 has The tunnel magnetoresistance (TMR) effect appears. In order to obtain a high magnetoresistance change rate, it is preferable to use the TMR effect. When utilizing the TMR effect, the thickness of the spacer layer 32 is preferably about 0.5 nm to 3.0 nm. If the film thickness is too thin, if a pinhole is generated in the spacer layer 32, a leakage current flows, which is not preferable. If the film thickness is too thick, the resistance value of the magnetoresistive effect element 3 increases, and therefore the difference between the impedance of the input terminal 1 and the impedance of the magnetoresistive effect element 3 increases. Therefore, impedance matching between the input terminal 1 and the magnetoresistive effect element 3 is difficult to take, and the frequency modulation signal input from the input terminal 1 is reflected by the magnetoresistive effect element 3, and the frequency modulation signal is reflected by the magnetoresistive effect element. 3 is not input enough.

Further, the spacer layer 32 may have a current confinement structure in which a current confinement path exists in the insulating layer. In this case, AlOx, MgO, or the like can be used as the insulating layer, and a non-magnetic conductive material such as Cu, Ag, Au, or Ru, an alloy of Fe and Co, an alloy of Fe, Co, and Al, as a current confinement path, A magnetic conductive material such as an alloy of Fe, Co, Al, and Si can be used.

The magnetization free layer 33 has a function of changing the magnetization direction by a magnetic field generated from the magnetic field application mechanism 5. The magnetization free layer 33 is preferably made of a high spin polarizability material such as Fe, Co, Ni, FeCo, or CoFeB. Thereby, a high magnetoresistance change rate can be obtained. FIG. 3 is a sectional view of the magnetoresistive element 3 shown in FIG. When the film thickness of the magnetization free layer 33 is t1 and the film thickness of the magnetization fixed layer 31 is t2, it is preferable that 0.4 nm <t1 <t2. When t1 becomes smaller than 0.4 nm, the saturation magnetization amount of the magnetization free layer 33 is remarkably reduced, so that the magnetoresistance change rate is remarkably reduced. When t1 becomes larger than t2, the spin torque acts not on the magnetization of the magnetization free layer 33 but on the magnetization of the magnetization fixed layer 31, so that the spin torque diode effect cannot be sufficiently obtained in the magnetization free layer 33.

Although not shown, a cap layer, a seed layer, or a buffer layer may be included between the lower electrode 2 and the magnetoresistive effect element 3 and between the magnetoresistive effect element 3 and the upper electrode 4. The cap layer, seed layer, or buffer layer is preferably composed of Ru, Ta, Cu, Cr, and a laminated film thereof.

The magnetic field application mechanism 5 applies a magnetic field to the magnetoresistive effect element 3. When a frequency modulation signal is input to the magnetoresistive effect element 3 in a state in which a magnetic field is applied to the magnetoresistive effect element 3, the magnetoresistive effect element 3 receives the first corresponding to the first frequency of the frequency modulation signal from the output terminal 7. The first output voltage and the second output voltage corresponding to the second frequency are output. Further, the magnetic field application mechanism 5 has a function of applying a magnetic field having such a magnitude that a voltage difference ΔV between the first output voltage and the second output voltage exists to the magnetoresistive element 3.

As shown in FIG. 1, the magnetic field application mechanism 5 includes a coil 51, a coil current source 511, and a soft magnetic layer 52. Further, the coil 51 is wound around the soft magnetic layer 52. In this case, when a current is passed from the coil current source 511 to the coil 51, a magnetic flux proportional to the current is generated in the coil 51, and this magnetic flux propagates to the soft magnetic layer 52 and is arranged in the vicinity of the magnetoresistive effect element 3. A magnetic field concentrated at the tip of the soft magnetic layer 52 and generated from the tip of the soft magnetic layer 52 is applied to the magnetoresistive element 3.

The coil 51 is preferably made of a highly conductive material such as Au, Cu, or AuCu. This makes it possible to reduce the current flowing through the coil 51 in order to obtain a desired magnetic field. The soft magnetic layer 52 is preferably made of a NiFe alloy such as NiFe or NiFeCo, or a material having low coercive force and high saturation magnetization characteristics such as an FeCo alloy. As a result, more magnetic flux generated in the coil 51 can be taken into the soft magnetic layer 52, so that the magnetic field applied to the magnetoresistive element 3 can be increased.

  In the first embodiment, as shown in FIGS. 4A and 4B, the magnetic field application mechanism 5 changes the ferromagnetic resonance frequency (f0) of the magnetization of the magnetization free layer 33 to the first frequency (f1) and the second frequency. A magnetic field having such a magnitude that either one of (f2) (f2 in the examples shown in FIGS. 4A and 4B) and the ferromagnetic resonance frequency (f0) of the magnetization of the magnetization free layer 33 coincide with each other is applied. Apply to. As a result, the second output voltage corresponding to the second frequency can be increased. Therefore, the voltage difference ΔV between the first output voltage corresponding to the first frequency of the frequency modulation signal and the second output voltage corresponding to the second frequency can be increased.

The magnetic field application mechanism 5 can variably control the magnetic field applied to the magnetoresistive element 3 by adjusting the amount of current flowing through the coil 51. Therefore, the frequency characteristic of the spin torque diode effect of the magnetoresistive effect element 3 can be controlled in a tunable manner. This will be described with reference to FIGS. 4A and 4B. For example, when the second frequency (f2) of the frequency modulation signal is relatively low, the magnetization of the magnetization free layer 33 can be reduced by reducing the current flowing through the coil 51 and reducing the magnetic field applied to the magnetoresistive effect element 3. The ferromagnetic resonance frequency f0 can be set low. As a result, as shown in FIG. 4A, the ferromagnetic resonance frequencies f0 and f2 of the magnetization of the magnetization free layer 33 can be matched. On the other hand, when the second frequency (f2) of the frequency modulation signal is relatively high, the current flowing through the coil 51 is increased to increase the magnetic field applied to the magnetoresistive effect element 3, whereby the magnetization of the magnetization free layer 33 is increased. The ferromagnetic resonance frequency f0 can be set high. As a result, as shown in FIG. 4B, the ferromagnetic resonance frequencies f0 and f2 of the magnetization of the magnetization free layer 33 can be matched. Therefore, even if f2 changes to some extent, f2 and f0 can be matched, so that the second output voltage corresponding to f2 can be increased. Therefore, the voltage difference ΔV between the first output voltage corresponding to the first frequency of the frequency modulation signal and the second output voltage corresponding to the second frequency can be increased. Further, even if f2 and f0 are matched, and both frequencies are shifted due to the influence of disturbance or the like, the frequency of both can be matched again by adjusting the amount of current flowing through the coil 51 again. It becomes possible. Therefore, ΔV can be maintained in a large state even if it is affected by a disturbance or the like.

In the first embodiment, the magnetoresistive effect element 3 is provided with a magnetic field having such a magnitude as to match the second frequency (f2) of the frequency modulation signal and the ferromagnetic resonance frequency (f0) of the magnetization of the magnetization free layer 33. As described in the application example, the magnetoresistive effect element 3 applies a magnetic field having such a magnitude as to match the first frequency (f1) of the frequency modulation signal and the ferromagnetic resonance frequency (f0) of the magnetization of the magnetization free layer 33. You may make it apply to.

In the first embodiment, the coil 51 is used in the magnetic field application mechanism 5, but a wire may be used instead of the coil 51. In this case, a wire may be disposed near the soft magnetic layer 52 and the wire and the soft magnetic layer 52 may be magnetically connected.

The bias current application mechanism 6 has a function of applying a DC bias current from the bias current source 61 to the magnetoresistive element 3 via the lower electrode 2 and the upper electrode 4. FIG. 5 is a diagram showing the relationship between the bias current and the spin torque diode sensitivity. Here, the sign of the bias current is positive when a bias current is applied from the magnetization free layer 33 to the magnetization fixed layer 31 and negative when a bias current is applied from the magnetization fixed layer 31 to the magnetization free layer 33. As can be seen from FIG. 5, by applying the bias current, the sensitivity of the spin torque diode increases as compared with the case where the bias current is zero. Particularly, the spin torque diode sensitivity when the bias current is positive, that is, when the bias current is applied from the magnetization free layer 33 to the magnetization fixed layer 31 is negative, that is, the bias current from the magnetization fixed layer 31 to the magnetization free layer 33 is negative. It can be seen that the sensitivity is higher than the spin torque diode sensitivity when. This is because, when the bias current is positive, electrons spin-polarized by the magnetization fixed layer 31 are injected into the magnetization free layer 33, so that the spin transfer torque acting on the magnetization of the magnetization free layer 33 can be exerted more greatly. Because it becomes. By increasing the spin torque diode sensitivity, the voltage difference ΔV between the first output voltage and the second output voltage can be increased.

The output terminal 7 has a function of taking out a first output voltage corresponding to the first frequency generated in the magnetoresistive effect element 3 and a second output voltage corresponding to the second frequency. Since it has a function of detecting the output voltage output from the terminal 7, if there is a voltage difference ΔV between the first output voltage and the second output voltage, the first frequency component of the frequency modulation signal and the second It becomes possible to detect the frequency components separately. Therefore, when a frequency modulation signal including at least a first frequency (f1) component and a second frequency (f2) component different from f1 as shown in FIG. As shown in FIG. 6B, the unit 8 can detect the first output voltage (V1) corresponding to f1 and the second output voltage (V2) corresponding to f2.

That is, the detector 100 can detect the first output voltage corresponding to the first frequency component of the frequency modulation signal and the second output voltage corresponding to the second frequency component. . Therefore, if there is a voltage difference ΔV between the first output voltage and the second output voltage, the frequency modulation signal can be detected.

As described above, the detector 100 includes the magnetoresistive effect element 3 including the magnetization fixed layer 31 and the magnetization free layer 33 disposed via the spacer layer 32, and the magnetoresistance effect in the stacking direction of the magnetoresistive effect element 3. A pair of electrodes (lower electrode 2 and upper electrode 4) disposed via the effect element 3, a magnetic field application mechanism 5 that applies a magnetic field to the magnetoresistive effect element 3, and the magnetoresistive effect element 3 are at least first. An input terminal 1 for supplying a frequency modulation signal including a component of frequency (f1) and a component of a second frequency (f2) different from f1, an output terminal 7 for extracting an output voltage from the magnetoresistive element 3, A detection unit 8 for detecting an output voltage, the lower electrode 2 and the upper electrode 4 are electrically connected to the input terminal 1 and the output terminal 7, and the magnetic field application mechanism 5 has a first output corresponding to f1. Second corresponding to voltage and f2 Applying a size field, such as the voltage difference ΔV exists between the output voltage to the magnetoresistive element 3, the detection unit 8 detects the frequency-modulated signal based on the output voltage.

In the detector 100, the magnetic field application mechanism 5 applies a magnetic field having a magnitude such that there is a voltage difference ΔV between the first output voltage and the second output voltage to the magnetoresistive effect element 3, so that the voltage difference is increased. By using ΔV, it is possible to distinguish and detect the first frequency component and the second frequency component of the frequency modulation signal. Therefore, the frequency modulation signal can be detected with a relatively simple circuit configuration including the magnetoresistive element 3.

Furthermore, the detector 100 causes the magnetic field application mechanism 5 to match the ferromagnetic resonance frequency (f0) of the magnetization of the magnetization free layer 33 with one of the first frequency (f1) and the second frequency (f2). By applying a magnetic field having a large magnitude, it is possible to increase either the first output voltage or the second output voltage. Therefore, the voltage difference ΔV between the first output voltage and the second output voltage can be increased.

Further, the detector 100 can tunably control the frequency characteristics of the spin torque diode effect of the magnetoresistive effect element 3 by variably controlling the magnetic field applied to the magnetoresistive effect element 3 by the magnetic field applying mechanism 5. It becomes possible. Therefore, even if the first frequency (f1) or the second frequency (f2) of the frequency modulation signal changes to some extent, the components of the first frequency (f1) and the second frequency (f2) of the frequency modulation signal One of the components can be matched with the ferromagnetic resonance frequency (f0) of the magnetization of the magnetization free layer 33, and the voltage difference ΔV between the first output voltage and the second output voltage can be increased. Become.

Furthermore, the detector 100 includes the bias current application mechanism 6 that applies a DC bias current to the magnetoresistive effect element 3, so that the spin transfer torque acting on the magnetization of the magnetization free layer 33 can be increased. The diode sensitivity can be increased. Accordingly, the voltage difference ΔV corresponding to the frequency difference between the first frequency (f1) and the second frequency (f2) of the frequency modulation signal can be increased.

Further, in the detector 100, the bias current applied by the bias current applying mechanism 6 is applied in the direction from the magnetization free layer 33 to the magnetization fixed layer 31, so that electrons flow from the magnetization fixed layer 31 to the magnetization free layer 33. Thus, the spin transfer torque acting on the magnetization of the magnetization free layer 33 can be increased, and the spin torque diode sensitivity can be further increased. Therefore, the voltage difference ΔV between the first output voltage and the second output voltage can be further increased.

Furthermore, the detector 100 efficiently exhibits the spin torque diode effect by satisfying 0.4 nm <t1 <t2, where the thickness of the magnetization free layer 33 is t1 and the thickness of the magnetization fixed layer 31 is t2. It becomes possible to make it. Therefore, the voltage difference ΔV between the first output voltage and the second output voltage can be increased.

Although the present invention has been specifically shown and described with reference to preferred embodiments thereof, the present invention is not limited to those embodiments and is within the scope of the gist of the invention described in the claims. Various changes can be made.

  For example, in the first embodiment, the relationship between the film thickness t2 of the magnetization fixed layer 31 and the film thickness t1 of the magnetization free layer 33 is 0.4 nm <t1 <t2, but the present invention is not limited to this. In this case, since the spin torque diode effect cannot be sufficiently obtained in the magnetization free layer 33 as compared with the first embodiment, the first output voltage and the second output voltage become small, and therefore the first output voltage. The voltage difference ΔV between the first output voltage and the second output voltage is also reduced, but it is possible to detect the first frequency component and second frequency component of the frequency modulation signal separately.

  For example, although the bias current is positive in the first embodiment, the bias current may be negative, that is, the bias current may be applied in the direction from the magnetization fixed layer 31 to the magnetization free layer 33. In this case, as shown in FIG. 5, since the sensitivity of the spin torque diode is lowered as compared with the first embodiment, the first output voltage and the second output voltage are reduced, and therefore the first output voltage and Although the voltage difference ΔV from the second output voltage is also small, it is possible to detect the first frequency component and the second frequency component of the frequency modulation signal separately.

  For example, in the first embodiment, the bias current application mechanism 6 is provided, but the bias current application mechanism 6 may not be provided. In this case, since a bias current cannot be applied to the magnetoresistive effect element 3, as shown in FIG. Therefore, compared with the first embodiment, the first output voltage and the second output voltage are reduced, and thus the voltage difference ΔV between the first output voltage and the second output voltage is also reduced, but the frequency modulation is performed. It is possible to distinguish and detect the first frequency component and the second frequency component of the signal.

For example, in the first embodiment, the magnetic field application mechanism 5 includes the coil 51 and the soft magnetic layer 52, but the detector 102 according to the second embodiment of the present invention shown in the schematic diagram of FIG. As described above, the magnetic field application mechanism 5 may be configured by the hard bias layer 53. The detector 102 has the same configuration as the detector 100 of the first embodiment except for the magnetic field application mechanism 5.

Here, the hard bias layer 53 may be made of a CoPtCr alloy, a CoPt alloy, or the like, or may be made of an exchange coupling film made of a soft magnetic material and an antiferromagnetic material.

In this case, since the magnetic field (Hext) to be applied to the magnetoresistive effect element 3 can be set by appropriately designing the material and shape of the hard bias layer 53, the magnetization free as described in the equation (1). The ferromagnetic resonance frequency (f0) of the magnetization of the layer 33 can be set. Therefore, as an example, the second frequency (f2) of the frequency modulation signal can be matched with the ferromagnetic resonance frequency (f0) of the magnetization of the magnetization free layer 33. As a result, the second output voltage corresponding to the second frequency can be set to the same level as in the first embodiment. Therefore, the voltage difference ΔV between the first output voltage corresponding to the first frequency of the frequency modulation signal and the second output voltage corresponding to the second frequency can be set to the same level as in the first embodiment. It becomes.

Further, for example, in the first embodiment, the magnetic field application mechanism 5 is configured so that the second frequency (f2) of the frequency modulation signal matches the ferromagnetic resonance frequency (f0) of the magnetization of the magnetization free layer 33. Although a magnetic field is applied to the effect element 3, it is not necessary to make f2 and f0 coincide. FIG. 8 shows the relationship between the output voltage and the frequency in the third embodiment of the present invention. In the third embodiment, the magnetic field application mechanism 5 has a voltage difference ΔV between the first output voltage corresponding to the first frequency (f1) of the frequency modulation signal and the second output voltage corresponding to f2. A magnetic field having such a magnitude is applied to the magnetoresistive element 3, but f1 and f2 do not coincide with f0. The detector of the third embodiment has the same configuration as that of the detector 100 of the first embodiment, except for the magnetic field applied by the magnetic field application mechanism 5. As shown in FIG. 8, a magnetic field having such a magnitude that there is a voltage difference ΔV between the first output voltage corresponding to the first frequency (f1) of the frequency modulation signal and the second output voltage corresponding to f2. As long as it is applied to the magnetoresistive effect element 3, the magnetic field applied to the magnetoresistive effect element 3 does not have to be a magnetic field in which f0 matches one of f1 and f2. In this case, the first output voltage and the second output voltage are smaller than in the first embodiment, and thus the voltage difference ΔV between the first output voltage and the second output voltage is also smaller. It is possible to distinguish and detect the first frequency component and the second frequency component of the modulation signal.

Also in the third embodiment, the frequency characteristic of the spin torque diode effect of the magnetoresistive effect element 3 can be tunably controlled by variably controlling the magnetic field applied to the magnetoresistive effect element 3 by the magnetic field application mechanism 5. Is possible. Therefore, even if the first frequency (f1) and the second frequency (f2) of the frequency modulation signal change to some extent, the first output voltage and the second output voltage required for detection are changed according to the change. The magnetic field applying mechanism 5 changes the magnetic field applied to the magnetoresistive effect element 3 so that a voltage difference ΔV with respect to the output voltage of the first frequency component of the frequency modulation signal is obtained. It is possible to detect the component separately.

Further, the first embodiment is described with an example in which a frequency modulation signal including two different frequency components of the first frequency (f1) and the second frequency (f2) is supplied to the magnetoresistive effect element 3. However, the frequency modulation signal supplied to the magnetoresistive effect element 3 may include three or more different frequency components. In this case, the magnetic field applying mechanism 5 applies a magnetic field having a magnitude different from the output voltage from the magnetoresistive effect element 3 corresponding to each frequency to the magnetoresistive effect element 3, so that the component of each frequency is obtained. It can be distinguished and detected.

DESCRIPTION OF SYMBOLS 1 Input terminal 12 Ground terminal 2 Lower electrode 3 Magnetoresistive element 31 Magnetization fixed layer 32 Spacer layer 33 Magnetization free layer 4 Upper electrode 5 Magnetic field application mechanism 51 Coil 511 Coil current source 52 Soft magnetic layer 53 Hard bias layer 6 Bias current application Mechanism 61 Bias current source 7 Output terminal 72 Ground terminal 8 Detector 100, 102 Detector

Claims (6)

A magnetoresistive effect element comprising a magnetization fixed layer and a magnetization free layer disposed via a spacer layer;
A pair of electrodes disposed via the magnetoresistive element in the stacking direction of the magnetoresistive element;
A magnetic field application mechanism for applying a magnetic field to the magnetoresistive element;
An input terminal that supplies a frequency modulation signal including at least a first frequency component and a second frequency component different from the first frequency to the magnetoresistive element;
An output terminal for extracting an output voltage from the magnetoresistive element, and a detection unit for detecting the output voltage,
The pair of electrodes are electrically connected to the input terminal and the output terminal,
The magnetic field application mechanism has a voltage difference between a first output voltage as the output voltage corresponding to the first frequency and a second output voltage as the output voltage corresponding to the second frequency. Applying the magnetic field of such a magnitude,
Based on the output voltage, the first frequency component and the second frequency component of the frequency modulation signal are distinguished and detected , and the first frequency component detection and the second frequency component are detected. The detection is performed in a state where the same magnetic field is applied to the magnetoresistive effect element . The magnetic field application mechanism applies the magnetic field having a magnitude that causes a ferromagnetic resonance frequency of magnetization of the magnetization free layer to coincide with one of the first frequency and the second frequency. The detector according to claim 1. The detector according to claim 1, wherein the magnetic field application mechanism variably controls a magnetic field applied to the magnetoresistive effect element. The said detector has a bias current application mechanism which applies a bias current to the said magnetoresistive effect element, The detector as described in any one of Claim 1 to 3 characterized by the above-mentioned. The detector according to claim 4, wherein the bias current is applied in a direction from the magnetization free layer to the magnetization fixed layer. The film thickness of the magnetization free layer is t1, and the film thickness of the magnetization fixed layer is t2, satisfying 0.4 nm <t1 <t2. Detector.

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