WO2013180277A1

WO2013180277A1 - Oscillator

Info

Publication number: WO2013180277A1
Application number: PCT/JP2013/065217
Authority: WO
Inventors: 諭家形; 崇木村; 周太本多
Original assignee: 国立大学法人九州大学
Priority date: 2012-05-31
Filing date: 2013-05-31
Publication date: 2013-12-05
Also published as: JPWO2013180277A1

Abstract

Provided is an oscillator provided with a function enabling high frequency oscillation, a high Q value, and high heat stability through the use of a magnetic-vortex structure and interlayer exchange coupling. The present invention is provided with: a fixed layer (11) comprising a magnetic body of fixed magnetization having a magnetic-vortex structure vertically magnetized in the center portion; a non-magnetic layer (12) comprising a non-magnetic body laminated on the fixed layer (11); a free layer (13) laminated on the nonmagnetic layer (12) and having vertical magnetization rotatably moving in the planar direction, the free layer (13) comprising a strongly magnetic body having a magnetic-vortex structure of circular or regularly polygonal planar configuration that is vertically magnetized in the center portion; and a current-supply unit (16) for sending a current through the layers. The oscillator oscillates using the relative difference in angle between the magnetization in the fixed layer (11) and the central magnetization of the free layer (13). The free layer (13) is composed of a plurality of strongly magnetic free layers coupled using interlayer exchange coupling.

Description

Oscillating element

The present invention relates to an oscillation element using the frequency characteristics of a magnetic vortex structure.

A three-dimensional mounting technique in which semiconductor chips are stacked three-dimensionally has been proposed as a technique for realizing further high integration of electronic devices. In this case, since data is transferred between the stacked semiconductor chips by wireless communication, the development of a nano-sized high-frequency oscillation element that can be loaded on an integrated circuit is the key to realizing three-dimensional mounting. As the most promising candidate, a nonmagnetic layer made of a nonmagnetic material is sandwiched between two ferromagnetic layers made of a ferromagnetic material (a fixed layer and a free layer), and a direct current is applied between the ferromagnetic layers and a magnetic field is applied simultaneously. Thus, a spin torque generator (STO: Spin-Torque-Oscillator) that oscillates microwaves by self-excitation by rotating the magnetization of the free layer has been proposed (see FIG. 14). This STO is very small (<1 μm) and has a simple structure. However, since it cannot produce a high output and its thermal stability is not good, it is desired to develop an oscillation element having high output and high thermal stability.

Magnetic vortex structure that forms a magnetic vortex in the circumferential direction of the disk by forming the ferromagnetic material into a minute disk shape and forms a perpendicular magnetization (core) in the vertical direction of the disk at the center. It has been known. A technique is disclosed in which the core rotates by changing its position by a magnetic field or current applied from the outside (see, for example, Patent Document 1). This magnetic vortex structure has excellent frequency characteristics due to stable magnetization regardless of the material. As a technique related to the simulation of magnetic vortices, a technique shown in Non-Patent Document 1 is known.

In addition, the non-magnetic layer made of a non-magnetic material is sandwiched between two ferromagnetic layers made of a ferromagnetic material, and interlayer exchange coupling in which the direction and strength of the ferromagnetic layer change depending on the film thickness of the non-magnetic material is known. (For example, see Non-Patent Documents 2-4). By this interlayer exchange coupling, very high thermal stability can be realized. Moreover, a tunnel magnetoresistive element using interlayer exchange coupling is disclosed (see, for example, Patent Document 2).

Furthermore, a technique relating to an oscillation element using a magnetic vortex structure is disclosed (for example, see Non-Patent Documents 5 and 6). These technologies have an advantage in output by using a tunnel barrier.

JP 2009-76119 A JP 2010-80920 A

As shown above, the currently known STO has poor thermal stability of the ferromagnetic material when it is miniaturized, so that the Q value, the oscillation output, and the S / N ratio due to this decrease. This is a problem.

Further, although Non-Patent Documents 5 and 6 disclose a technique related to an oscillation element using a magnetic vortex, there is a problem that an external magnetic field is considerably large and is not practical. In addition, it is necessary to generate a magnetic vortex in the free layer, but in order to generate a magnetic vortex, the diameter and thickness of the free layer must be adjusted appropriately, the size is limited and the degree of freedom in the shape is lost. It has the problem that it ends up.

The present invention provides an oscillation element having a high Q value with excellent frequency characteristics and high thermal stability using a magnetic vortex structure. In addition, an oscillation element having a function capable of high thermal stability and high frequency oscillation using interlayer exchange coupling is provided.

An oscillation element according to the present invention includes a fixed layer made of a ferromagnetic material having a magnetic vortex structure in which magnetization is fixed and first perpendicular magnetization is formed by a magnetic vortex, and a nonmagnetic layer provided on the fixed layer. A nonmagnetic layer made of a body, and a ferromagnetic material having a magnetic vortex structure formed by being stacked on the nonmagnetic layer and having a second perpendicular magnetization formed by a magnetic vortex, wherein the second perpendicular magnetization is a surface A free layer that rotates and moves in a direction, and current supply means that conducts current across each of the layers, and the first perpendicular magnetization in the fixed layer and the position of the first perpendicular magnetization in the free layer Oscillation is performed using a relative angle difference from the magnetization at the corresponding position.

Thus, in the oscillation element according to the present invention, a fixed layer made of a ferromagnetic material having a magnetic vortex structure in which magnetization is fixed and perpendicular magnetization is formed by a magnetic vortex, and a nonmagnetic layer made of a nonmagnetic material, And a free layer in which perpendicular magnetization is rotated and moved in the plane direction. The perpendicular magnetization of the free layer is conducted by passing a current through each layer. Oscillates with an angular difference between the perpendicular magnetization in the fixed layer and the magnetization at the corresponding position in the free layer corresponding to the position of the perpendicular magnetization in the fixed layer. There exists an effect that an element is realizable.

In addition, since the fixed layer and the free layer have a magnetic vortex structure, stable magnetization can be formed without depending on the material, and by selecting a material capable of high output, high output can be achieved. There is an effect that an oscillation element can be realized. In addition, the magnetic vortex structure can achieve a high Q value, and the thermal stability can be enhanced by stable magnetization.

Furthermore, since the perpendicular magnetization due to the magnetic vortex is formed in the fixed layer and the free layer, the influence of the leakage magnetic field in the outer direction (outer peripheral direction) on each layer is not affected on the Q value, and a high-performance oscillation element is realized. There is an effect that can be.

In the oscillation element according to the present invention, the planar shape of the free layer is a circle or a regular polygon.
As described above, in the oscillation element according to the present invention, since the planar shape of the free layer is a circle or a regular polygon, a single perpendicular magnetization is formed with a stable structure, and an oscillation element having a configuration easy to control is realized. There is an effect that can be done.

In the oscillation element according to the present invention, the free layer is sandwiched between a plurality of ferromagnetic free layers made of a conductive ferromagnetic material having the magnetic vortex structure and the plurality of ferromagnetic free layers. And a plurality of nonmagnetic free layers made of a nonmagnetic material, and each of the layers is interlayer exchange coupled.

Thus, in the oscillation element according to the present invention, the free layer is a plurality of ferromagnetic free layers made of a ferromagnetic material having a magnetic vortex structure, and a plurality of nonmagnetic free layers made of a conductive nonmagnetic material are provided. Since the layers are sandwiched and the layers are exchange-exchange coupled, there is an effect that very high thermal stability can be realized according to the coupling strength.

In the oscillation element according to the present invention, the free layer has a first ferromagnetic free layer made of a ferromagnetic material having the magnetic vortex structure, and a non-conductive conductive layer provided on the first ferromagnetic free layer. A non-magnetic free layer made of a magnetic material, a second ferromagnetic free layer provided on the non-magnetic free layer by being laminated, and made of a ferromagnetic material having the magnetic vortex structure, and being interlayer-exchange coupled with each of the layers It is what has.

As described above, in the oscillation element according to the present invention, the free layer includes the first ferromagnetic free layer and the second ferromagnetic free layer made of a ferromagnetic material having a magnetic vortex structure, and is made of a conductive nonmagnetic material. Since the nonmagnetic free layer is sandwiched and the layers are interlayer exchange coupled, an extremely high thermal stability can be achieved according to the coupling strength.

The oscillation element according to the present invention includes a rotation phase of perpendicular magnetization in the first ferromagnetic free layer and rotation of perpendicular magnetization in the second ferromagnetic free layer according to the coupling strength of interlayer exchange coupling in the free layer. The phase of rotation of the perpendicular magnetization in the first ferromagnetic free layer and the phase of rotation of the perpendicular magnetization in the second ferromagnetic free layer are different from each other. This is a high frequency oscillation mode that is a phase.

As described above, in the oscillation element according to the present invention, the rotation direction of the perpendicular magnetization in the first ferromagnetic free layer and the perpendicular magnetization in the second ferromagnetic free layer according to the coupling strength of the interlayer exchange coupling in the free layer. Since the phase of the rotation is the same as the low frequency mode or the different high frequency mode, the oscillation in the two modes can be realized.

An oscillation element according to the present invention includes a fixed layer made of a ferromagnetic material whose magnetization is fixed, a nonmagnetic layer made of a conductive nonmagnetic material provided on the fixed layer, and a nonmagnetic layer. It is made of a ferromagnetic material that is provided in a stacked manner and has perpendicular magnetization formed by magnetic vortices generated by energization. The formed perpendicular magnetization rotates and moves in the plane direction, and current is passed through each layer. Current supply means, and oscillates using a relative angle difference between magnetization at a predetermined position in the fixed layer and magnetization at a corresponding position corresponding to the position in the free layer.

Thus, in the oscillation element according to the present invention, since the nonmagnetic layer is made of a conductive nonmagnetic material, the magnetic vortex is formed in the free layer and the perpendicular magnetization is rotated by energization from the current supply means. Thus, there is an effect that an oscillating element having a high degree of freedom can be realized without being limited by the diameter and thickness of the layer.

In the oscillation element according to the present invention, the fixed layer is made of a ferromagnetic material in which perpendicular magnetization is formed by a magnetic vortex generated by energization, and the perpendicular magnetization in the fixed layer and the correspondence in the free layer corresponding to the perpendicular magnetization Oscillation is performed using a relative angle difference between the position magnetization and the position magnetization.

As described above, in the oscillation element according to the present invention, since the fixed layer has a magnetic vortex structure when energized in the same manner as the free layer, an oscillation element having excellent frequency characteristics can be realized by the magnetic vortex structure. There is an effect.

In the oscillating device according to the present invention, the free layer is sandwiched between a plurality of ferromagnetic free layers made of a ferromagnetic material in which perpendicular magnetization is formed by a magnetic vortex generated by energization, and the plurality of ferromagnetic free layers. And a plurality of nonmagnetic free layers made of a conductive nonmagnetic material, and each of the layers is interlayer exchange coupled.

Thus, in the oscillation element according to the present invention, the free layer is a plurality of ferromagnetic free layers made of a ferromagnetic material in which perpendicular magnetization is formed by magnetic vortices generated by energization, and a plurality of non-magnetic materials made of non-magnetic material. Since the magnetic free layer is sandwiched and each layer is interlayer exchange coupled, there is an effect that very high thermal stability can be realized according to the coupling strength.

1 is a first diagram illustrating a structure of an oscillation element according to a first embodiment. It is a 2nd figure which shows the structure of the oscillation element which concerns on 1st Embodiment. It is a figure which shows operation | movement of the oscillation element which concerns on 1st Embodiment. It is a figure which shows the structure of the oscillation element which concerns on 2nd Embodiment. 6 is a first diagram illustrating interlayer exchange coupling in an oscillation element according to a second embodiment. FIG. It is a 2nd figure which shows the interlayer exchange coupling in the oscillation element which concerns on 2nd Embodiment. It is a figure which shows operation | movement of the oscillation element which concerns on 2nd Embodiment. It is a figure which shows the frequency mode of the oscillation element which concerns on 2nd Embodiment. It is a figure which shows the observation experiment of the resonance in a magnetic vortex. It is a figure which shows the result of the observation experiment of the resonance in a magnetic vortex. It is a 1st figure which shows the resonance simulation of the magnetic vortex by interlayer exchange coupling. It is a 2nd figure which shows the resonance simulation of the magnetic vortex by interlayer exchange coupling. It is a figure which shows the experimental result by the element of a 225 nm x 500 nm size. It is a figure which shows the structure of the conventional STO.

Hereinafter, embodiments of the present invention will be described. The present invention can be implemented in many different forms. Also, the same reference numerals are given to the same elements throughout the present embodiment.

(First embodiment of the present invention)
The oscillation element according to this embodiment will be described with reference to FIGS. FIG. 1 is a first diagram illustrating the structure of an oscillation element according to the present embodiment, FIG. 2 is a second diagram illustrating the structure of the oscillation element according to the present embodiment, and FIG. 3 is an oscillation according to the present embodiment. It is a figure which shows operation | movement of an element.

As shown in FIG. 1A, the oscillation element according to this embodiment includes a fixed layer 11 made of a disk-shaped ferromagnetic material whose magnetization is fixed, and a disk provided by being laminated on the fixed layer 11. A non-magnetic layer 12 made of a non-magnetic material and a free layer 13 made of a disk-like ferromagnetic material. The free layer 13 has a magnetic vortex structure in which perpendicular magnetization (magnetization in a direction perpendicular to the plane direction of the free layer 13) is formed at the center portion. That is, the magnetization vortexes along the circumferential direction of the free layer 13 and rises in the vertical direction near the center of the disk.

When a magnetic field is applied in the radial direction to the free layer 13 having such a magnetic vortex structure, the position of the perpendicular magnetization can be changed. When the application of the magnetic field is stopped, the perpendicular magnetization is brought to the center position while performing a spiral motion. Return. Such control can also be performed by supplying a current. In the present embodiment, as shown in FIG. 1B, the current is supplied by the current supply unit 16 through the

electrodes

14 and 15 provided in the free layer 13 and the fixed layer 11, so that the vertical in the free layer 13 is obtained. Change the position of magnetization. That is, the perpendicular magnetization is rotationally moved in the plane direction of the free layer while maintaining the perpendicularity of the perpendicular magnetization.

In general, whether or not a magnetic vortex structure is formed depends on the ratio between the diameter and thickness of the magnetic material. That is, for example, in the techniques described in Non-Patent Documents 5 and 6, in order for the free layer 13 to have a magnetic vortex structure, restrictions on the diameter and thickness of the magnetic material are imposed, and the size and shape are free. The degree was low.

On the other hand, in the oscillation element 1 shown in FIG. 1A, the nonmagnetic layer 12 may be a conductive nonmagnetic material instead of an insulating material. That is, for example, in the techniques described in Non-Patent Documents 5 and 6, an MgO-based tunnel barrier is used for the nonmagnetic layer 12, whereas in the oscillation element according to the present embodiment, the nonmagnetic layer 12 is used. By forming a conductive non-magnetic material, a magnetic vortex structure is formed in the free layer with a magnetic field generated by applying a current from the current supply unit 16 regardless of the diameter, thickness, shape, etc. of the magnetic material. be able to. That is, the oscillation element 1 shown in FIG. 1A can freely set the size and shape of the element (see examples described later).

The pinned layer 11 has a fixed magnetization. In the case of FIG. 1A, the pinned layer 11 is pinned in the plane direction (a direction parallel to the plane of the pinned layer 11), and in the case of FIG. In the same manner as above, the magnetic vortex structure is fixed at the center position in the vertical direction (direction perpendicular to the surface of the fixed layer 11). Since the magnetization of the fixed layer 11 is fixed, it does not change even when a current is applied, and only the magnetization of the free layer 13 changes. As shown in FIG. 1A, when the magnetization of the fixed layer 11 is fixed in the horizontal direction, the perpendicular magnetization of the free layer 13 can be moved efficiently, whereas in FIG. As shown, when the magnetization of the fixed layer 11 is fixed in the vertical direction, the magnetization is stabilized by the magnetic vortex structure, and excellent frequency characteristics can be realized.

Note that, as shown in FIG. 2B, the supply of current is the same as in FIG. 1B. Also in the oscillation element 1 of FIG. 2, it is possible to increase the degree of freedom of the element size and shape by making the nonmagnetic layer conductive as in the case of FIG.

In the present embodiment, the perpendicular magnetization of the free layer 13 rotates and moves in the plane direction, thereby oscillating by the relative angle difference between the magnetization of the free layer 13 and the fixed magnetization of the fixed layer 11. For example, by using a relative angular difference between the magnetization of the center portion of the free layer 13 and the fixed magnetization (horizontal magnetization in the case of FIG. 1 and vertical magnetization in the case of FIG. 2) in the fixed layer 11. Realize oscillation. FIG. 3 shows an example of the oscillation operation. In FIG. 3, the fixed layer 11 has a magnetic vortex structure, and is fixed by forming perpendicular magnetization at the central portion. Similarly, the free layer 13 is also perpendicularly magnetized at the center portion by the magnetic vortex structure, but the magnetization is not fixed, and the current layer 16 rotates and moves in the plane direction when the current is supplied by the current supply unit 16. At this time, it rotates and moves while maintaining the perpendicularity of the perpendicular magnetization.

3A shows the state of the oscillation element 1 when the rotation angle of perpendicular magnetization is 0 degrees (or 360 degrees), and FIG. 3B shows the oscillation when the rotation angle of perpendicular magnetization is 90 degrees. FIG. 3C shows the state of the element 1, FIG. 3C shows the state of the oscillation element 1 when the rotation angle of perpendicular magnetization is 180 degrees, and FIG. 3D shows the case where the rotation angle of perpendicular magnetization is 270 degrees. The state of the oscillation element 1 is shown.

As shown in FIGS. 3A to 3D, the vertical magnetization rotates and moves in the plane direction, so that the position of the free layer 13 corresponding to the perpendicular magnetization of the fixed layer 11 (that is, according to the rotation angle (ie, The direction of the magnetic vortex of the free layer 13 in the central portion of the free layer 13 changes periodically. Oscillation can be performed by the difference in relative angle between the magnetization of the fixed layer 11 and the magnetization of the free layer 13.

In the oscillation element 1, the shape of each layer is formed in a disk shape, but may be any shape as long as one perpendicular magnetization is stably formed by the magnetic vortex structure. The shape formed by a square, an ellipse, and several other closed line segments may be sufficient. In the case of a disc shape or a regular polygon shape, a single perpendicular magnetization can be stably formed, and control becomes easy. Further, when the shape has an edge, the potential of the magnetic vortex increases at the edge portion, and the frequency can be increased. Furthermore, in the case of other complicated shapes or long shapes, a plurality of magnetic vortex structures can be formed, and oscillation at various frequencies and intensities can be performed.

In particular, as described above, when the nonmagnetic layer 12 is made of a conductive nonmagnetic material and a magnetic vortex is generated by a magnetic field caused by energization, there is no need to consider the direct system or thickness limitation at all. Can be set freely.

Furthermore, the direction of rotation of the magnetic vortex may be either clockwise or counterclockwise.

Thus, according to the oscillation element according to the present embodiment, it is possible to realize an oscillation element having excellent frequency characteristics due to the magnetic vortex structure and to form stable magnetization without depending on the material. Therefore, by selecting a material capable of high output (for example, a material called a half metal such as Co 2 FeSi or Co 2 MnSi having a high spin polarization rate), a high output oscillation element can be realized. In addition, a high Q value can be realized by the magnetic vortex structure, and thermal stability can be enhanced by stable perpendicular magnetization.

(Second embodiment of the present invention)
The oscillation element according to this embodiment will be described with reference to FIGS. 4 is a diagram illustrating the structure of the oscillation element according to the present embodiment, FIG. 5 is a first diagram illustrating interlayer exchange coupling in the oscillation element according to the present embodiment, and FIG. 6 is an oscillation element according to the present embodiment. FIG. 7 is a diagram illustrating the operation of the oscillation element according to the present embodiment, and FIG. 8 is a diagram illustrating the frequency mode of the oscillation element according to the present embodiment.
In addition, in this embodiment, the description which overlaps with the said 1st Embodiment is abbreviate | omitted.

The oscillation element according to the present embodiment achieves very high thermal stability by using interlayer exchange coupling for the free layer 13 of the oscillation element according to the first embodiment. Further, by controlling the frequency mode using the structure of the interlayer exchange coupling of the free layer 13, oscillation at a very high frequency is realized.

As shown in FIG. 4, the oscillation element 1 according to this embodiment includes a first ferromagnetic free layer in which the free layer 13 of the oscillation element 1 according to the first embodiment is made of a ferromagnetic material having a magnetic vortex structure. 13a, a nonmagnetic free layer 13b made of a conductive nonmagnetic material (for example, Ru, Cu, Cr, etc.) provided to be stacked on the first ferromagnetic free layer, and a nonmagnetic free layer 13b. The second ferromagnetic free layer 13c is provided and is made of a ferromagnetic material having a magnetic vortex structure, and has a first ferromagnetic free layer 13a and an interlayer exchange coupling.

The interlayer exchange coupling between the first ferromagnetic free layer 13a and the second ferromagnetic free layer 13c will be described in detail. FIG. 5 shows the relationship between the film thickness of the nonmagnetic free layer 13b and the coupling strength and coupling direction of the first ferromagnetic free layer 13a and the second ferromagnetic free layer 13c. As shown in FIG. 5, as the film thickness of the nonmagnetic free layer 13b increases, the coupling strength between the first ferromagnetic free layer 13a and the second ferromagnetic free layer 13c decreases. Although details will be described later, the frequency mode is specified according to the magnitude of the coupling strength.

As shown in FIG. 5, the coupling direction (parallel / antiparallel) is specified by the film thickness of the nonmagnetic free layer 13b. In the oscillation element according to the present embodiment, the direction of coupling does not contribute to the frequency characteristics of oscillation and can be ignored, and the magnitude of coupling strength is an important factor.

FIG. 6 shows the thermal stability according to the film thickness of the nonmagnetic free layer 13b and the second ferromagnetic free layer 13c by interlayer exchange coupling. The value of d in the figure indicates the film thickness of the second ferromagnetic free layer 13c, and Δ0 indicates the thermal stability. The values shown in the table of FIG. 6 are reference values and are data when the in-plane magnetization is horizontal. As is apparent from the figure, Δ0 indicating thermal stability increases as the thickness of the second ferromagnetic free layer 13c increases. It can also be seen that when the thickness of the second ferromagnetic free layer 13c is the same, Δ0 increases as the thickness of the nonmagnetic free layer 13b increases. As described above, by using the interlayer exchange coupling as shown in FIGS. 5 and 6, it is possible to significantly improve the thermal stability.

In addition, the oscillation element according to the present embodiment realizes a high frequency by adjusting the coupling strength of the interlayer exchange coupling to an arbitrary value by using the free layer 13 having a plurality of ferromagnetic free layers. Can do. That is, when the perpendicular magnetization of the first ferromagnetic free layer 13a and the perpendicular magnetization of the second ferromagnetic free layer 13c rotate and move in the same phase, oscillation occurs in a low frequency mode (referred to as acoustic mode), and vice versa. When rotating and moving in phase, oscillation in a high frequency mode (referred to as an optical mode) is possible. An image of perpendicular magnetization in the optical mode is shown in FIG. FIG. 7 shows a state in which the perpendicular magnetization of the first ferromagnetic free layer 13a and the perpendicular magnetization of the second ferromagnetic free layer 13c are rotationally moved in opposite phases. FIG. 7A shows the state of perpendicular magnetization when the first ferromagnetic free layer 13a is 0 degrees (or 360 degrees) and the second ferromagnetic free layer 13c is 180 degrees, and FIG. FIG. 7C shows the state of perpendicular magnetization when the first ferromagnetic free layer 13a is 90 degrees and the second ferromagnetic free layer 13c is 270 degrees. FIG. 7C shows the first ferromagnetic free layer 13a at 180 degrees. FIG. 7D shows the state of perpendicular magnetization when the second ferromagnetic free layer 13c is 0 degrees (or 360 degrees). FIG. 7D shows the second ferromagnetic free layer when the first ferromagnetic free layer 13a is 270 degrees. The state of perpendicular magnetization when 13c is 90 degrees is shown. In each state, the perpendicular magnetization of the first ferromagnetic free layer 13a and the perpendicular magnetization of the second ferromagnetic free layer 13c are in opposite phases, realizing high frequency oscillation.

FIG. 8 shows an optical mode and an acoustic mode. When the perpendicular magnetization of the first ferromagnetic free layer 13a and the perpendicular magnetization of the second ferromagnetic free layer 13c rotate and move in the same phase, a low frequency is realized. When the perpendicular magnetization of the first ferromagnetic free layer 13a and the perpendicular magnetization of the second ferromagnetic free layer 13c rotate and move in opposite phases, a high frequency is realized. The difference between these frequencies is proportional to the coupling strength of the interlayer exchange coupling, and by adjusting the effective magnetic field between the layers, it becomes possible to realize oscillation at a higher frequency.

Thus, according to the oscillation element according to the present embodiment, since each layer in the free layer is interlayer exchange coupled, very high thermal stability can be realized depending on the coupling strength. Further, when the coupling strength of the interlayer exchange coupling in the free layer is a predetermined value, the rotation phase of the perpendicular magnetization in the first ferromagnetic free layer 13a and the rotation of the perpendicular magnetization in the second ferromagnetic free layer 13c. Therefore, the effective magnetic field between the layers increases, and oscillation at a high frequency can be realized.

In the present embodiment, the magnetization direction of the fixed layer 11 may be fixed in the plane direction of the fixed layer 11 as in the case of the first embodiment. Further, the free layer 13 may be three or more layers.

Further, in the present embodiment, as in the case of the first embodiment, by making the nonmagnetic layer 12 conductive, it is possible to increase the degree of freedom of the element size and shape.

The following experiment and simulation were performed on the oscillation element according to the present invention.

(1) Observation of resonance in magnetic vortex FIG. 9A shows a schematic diagram of this experimental system, and FIG. 9B shows a planar shape of the magnetic vortex element used in this experiment. FIG. 10A shows the resonance spectrum of the magnetic vortex in each planar shape, and FIG. 10B shows the resonance frequency for each planar shape. In this experiment, an alternating current was applied to the magnetic vortex element, and the magnetic vortex (vertical magnetization) was rotated by applying the magnetic field shown in FIG. 9A, and the resonance spectrum of the magnetic vortex element was observed. The signal was extracted using homodyne detection. In the experiment, as shown in FIG. 9B, a magnetic vortex element having a regular pentagonal shape, a square shape, a regular triangle shape, and a circular shape was used.

As shown in FIGS. 10A and 10B, a frequency peak is detected in each planar magnetic vortex element, and it can be confirmed that resonance due to the magnetic vortex occurs. That is, it can be understood that oscillation is possible not only with a magnetic vortex element having a circular planar shape but also with a regular polygonal shape due to a magnetic vortex.

(2) Resonance simulation of magnetic vortex by interlayer exchange coupling FIG. 11A shows a free layer used in this simulation, and FIG. 11B shows a simulation result. Here, a high-frequency magnetic field was applied in-plane to a sample in which two magnetic layers having a magnetic vortex structure were interlayer-exchange coupled, and the resonance of the magnetic vortex was simulated. That is, since the frequency in the resonance state substantially coincides with the frequency in the oscillation state, the frequency during oscillation can be estimated by simulating the resonance state.

As shown in FIG. 11 (A), a permalloy thin film having a length of 150 nm and a width of 150 nm provided with a 10 nm gap (vacuum layer) facing each other was used. Here, the magnetic field (demagnetizing field) produced by the upper layer (or lower layer) does not affect the lower layer (or upper layer), and the exchange constant between the layers of the permalloy thin film is set to permalloy parameter × 0.05.

As shown in FIG. 11B (upper graph), the magnetization change was simulated by increasing the frequency by 0.1 GHz every 10 ns. From FIG. 11B, it was confirmed that resonance occurred at 0.7 GHz to 0.8 GHz and 1.3 GHz to 1.4 GHz. That is, it is shown that two modes (acoustic mode and optical mode) due to interlayer exchange coupling are excited.

Next, the resonance frequency was simulated by changing the exchange magnetic field between the two layers. FIG. 12A shows a free layer used in the simulation, and FIG. 12B shows a simulation result. As shown in FIG. 12A, a permalloy thin film having a length of 150 nm × width 150 nm provided with a 10 nm gap (vacuum layer) facing each other is used, and the exchange magnetic field at that time is defined as an exchange magnetic field ∝αKm / The simulation was performed as l2 (l = 10 nm when the vacuum layer was ignored, and l = 20 nm when the vacuum layer was considered: corresponding to α˜0.25).

As shown in FIG. 12B, when the distance between the cores (indicated by □) is small and the vibration radius of each core (indicated by ◯, ●) is large, the acoustic mode is set, and the distance between the cores is large. When the vibration radius of the core is small, the mode is the optical mode, and the resonance frequency in the optical mode changes according to the exchange energy between the two layers. In FIG. 12B, it is confirmed that the smaller the exchange energy between the two layers, the smaller the resonance frequency in the optical mode.

From the above, it was confirmed that the two-layer permalloy thin film having a magnetic vortex structure and coupled by interlayer exchange coupling resonates. That is, it is possible to realize an oscillation element that performs self-excited oscillation using these. Further, the smaller the exchange energy between the two layers (the longer the distance between the two layers), the closer the resonance frequency of the optical mode approaches the resonance frequency of the acoustic mode, and the greater the resonance. Further, the smaller the effective magnetic field between the two layers (the longer the distance between the two layers), the closer the resonance frequency of the optical mode approaches that of the acoustic mode, and the resonance increases. However, there is little influence compared with exchange energy, and adjustment of exchange energy is particularly important.

(3) Measured with 225 nm × 500 nm element FIG. 13A is a schematic diagram of this experimental system, FIG. 13B is a graph showing the dependence of the frequency on the current to be applied, and FIG. 13C is at 140 mA. It is a graph which shows the characteristic of a frequency. The free layer of the oscillation element used in this experiment is configured as a rectangular parallelepiped having a length of 225 nm, a width of 500 nm, and a thickness of 5 nm, and no magnetic vortex is formed in a normal state where no current flows. A direct current was passed through this element, and an alternating current output was observed with a spectrum analyzer.

As shown in FIG. 13B, the oscillation frequency changes according to the current, and the frequency increases as the current increases. This is a characteristic obtained at the time of oscillation due to the rotational movement of the magnetic vortex. As shown in FIG. 13C, for example, when a current of 140 mA is applied, a peak is detected at 2.87 GHz.

That is, from the results shown in FIGS. 13B and 13C, in the oscillation element according to the present invention, current is passed through a magnetic body having a size and shape that would normally prevent formation of a magnetic vortex. It is clear that a magnetic vortex is formed and can function as an oscillation element. Further, it is apparent that the frequency can be adjusted according to the current to be energized.

Thus, according to the oscillation element according to the present invention, high thermal stability and excellent frequency characteristics (high Q value) are realized by stable magnetization by the magnetic vortex structure, and higher thermal stability is achieved by interlayer exchange coupling. High-frequency oscillation in the optical mode can be realized. In addition, by using the magnetic vortex structure, stable perpendicular magnetization can be realized without depending on the material. Therefore, by selecting a material that can obtain a high output, a high output can be achieved.

DESCRIPTION OF SYMBOLS 1 Oscillator 11 Fixed layer 12 Nonmagnetic layer 13 Free layer 13a 1st ferromagnetic free layer 13b Nonmagnetic free layer 13c 2nd ferromagnetic

free layer

14,15 Electrode 16 Current supply part

Claims

A fixed layer made of a ferromagnetic material having a magnetic vortex structure in which the magnetization is fixed and the first perpendicular magnetization is formed by the magnetic vortex;
A nonmagnetic layer made of a nonmagnetic material provided to be laminated on the fixed layer;
A free layer that is provided by being laminated on the nonmagnetic layer and has a magnetic vortex structure in which second perpendicular magnetization is formed by a magnetic vortex, and wherein the second perpendicular magnetization rotates and moves in a plane direction; ,
Current supply means for energizing current over each of the layers,
Oscillation is performed using a relative angular difference between the first perpendicular magnetization in the fixed layer and the magnetization at a corresponding position corresponding to the position of the first perpendicular magnetization in the free layer. Oscillating element.
The oscillating device according to claim 1,
An oscillation element, wherein the planar shape of the free layer is a circle or a regular polygon.
In the oscillation element according to claim 1 or 2,
The free layer is
A plurality of ferromagnetic free layers made of a ferromagnetic material having the magnetic vortex structure;
A plurality of nonmagnetic free layers made of a conductive nonmagnetic material sandwiched between the plurality of ferromagnetic free layers,
An oscillation element, wherein each of the layers is interlayer exchange coupled.
The oscillation element according to claim 3,
The free layer is
A first ferromagnetic free layer made of a ferromagnetic material having the magnetic vortex structure;
A nonmagnetic free layer made of a conductive nonmagnetic material provided on the first ferromagnetic free layer;
The second magnetic free layer is provided by being laminated on the nonmagnetic free layer, is made of a ferromagnetic material having the magnetic vortex structure, and has a second ferromagnetic free layer that is exchange-coupled with each of the layers. Oscillating element.
In the oscillation element according to claim 4,
Depending on the value of the coupling strength of the interlayer exchange coupling in the free layer, the phase of the perpendicular magnetization rotation in the first ferromagnetic free layer and the phase of the perpendicular magnetization rotation in the second ferromagnetic free layer are in phase. Low-frequency oscillation mode, or high-frequency oscillation in which the phase of rotation of perpendicular magnetization in the first ferromagnetic free layer is different from the phase of rotation of perpendicular magnetization in the second ferromagnetic free layer An oscillation element characterized by being in a mode.
A fixed layer made of a ferromagnetic material whose magnetization is fixed;
A nonmagnetic layer made of a conductive nonmagnetic material provided to be laminated on the fixed layer;
A free layer provided by being laminated on the non-magnetic layer and made of a ferromagnetic material in which perpendicular magnetization is formed by a magnetic vortex generated by energization, and the formed perpendicular magnetization rotates and moves in a plane direction;
Current supply means for energizing current over each of the layers,
An oscillation element characterized in that oscillation is performed using a relative angle difference between magnetization at a predetermined position in the fixed layer and magnetization at a corresponding position corresponding to the position in the free layer.
The oscillation element according to claim 6,
The fixed layer is made of a ferromagnetic material in which perpendicular magnetization is formed by a magnetic vortex generated by energization,
An oscillation element that oscillates using a difference in relative angle between perpendicular magnetization in the fixed layer and magnetization at a corresponding position in the free layer corresponding to the perpendicular magnetization.
The oscillation element according to claim 6 or 7,
The free layer is
A plurality of ferromagnetic free layers made of a ferromagnetic material whose perpendicular magnetization is formed by magnetic vortices generated by energization;
A plurality of nonmagnetic free layers made of a conductive nonmagnetic material sandwiched between the plurality of ferromagnetic free layers,
An oscillation element, wherein each of the layers is interlayer exchange coupled.