JP2010245419A - Microwave oscillation element and microwave oscillation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave oscillation element and a microwave oscillation device, which oscillate microwaves with a simple element structure, without requiring a complicated film formation process and a microfabrication. <P>SOLUTION: The microwave oscillation element includes a laminated structure with a ferromagnetic layer 11 and a metal layer 12 having spin track interaction, wherein a current is flowed to the metal layer 12 by applying a voltage between terminals 13<SB>1</SB>and 13<SB>2</SB>at both ends of the metal layer from a power source 14 to implant a pure spin flow from the metal layer 12 to the ferromagnetic layer 11 through spin hole effect, thereby microwave oscillation is excited. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a microwave oscillating element and a microwave oscillating device, and relates to a structure for oscillating microwaves with a simple element configuration and a low current density.

  In the field of estronics such as current semiconductor devices, the degree of freedom of charge of electrons is used, but electrons have the degree of freedom of spin in addition to charges. In recent years, spintronics using this degree of freedom of spin has been attracting attention as a leader of next-generation information technology. This spintronics aims to obtain unprecedented functions and characteristics by simultaneously using the charge of electrons and the degree of freedom of spin.

  An example of such an initial device of spintronics is a GMR (giant magnetoresistive) element. The magnetization direction of the free layer depends on the spin of the electron that plays a role in the sense current flowing through the GMR element, that is, whether it is upspin or downspin. And the phenomenon in which the magnitude of the resistance changes under the influence of the difference between the magnetization direction of the pinned layer.

  In recent years, in MRAM (Magnetic Random Access Memory) using such a GMR element or TMR (Tunnel Magnetoresistive) element as a memory cell, the magnetization direction of the free layer is controlled by a magnetic field generated by passing a current through a wiring layer. A spin RAM has been proposed in which a current is directly applied to a GMR element or a TMR element, and the magnetization direction of the free layer is controlled by the spin of electrons serving as a current carrier (for example, Patent Document 1 or Patent Document 2). reference).

In such spintronics, the concept of spin relaxation is very important, and spin relaxation means attenuation of the motion of a spin or magnetic moment. The spin has a magnetic moment, and a macroscopic order appears as magnetization ^v M in the ferromagnet. Placing this magnetization ^v M in a magnetic field ^v H, interaction between the magnetic field ^v H acts as a torque on the magnetization, the magnetization will precess at a frequency determined by the magnetic field. In this case, for the purpose of preparing the specification, “ ^vM ” or “ ^vH ” is used for the notation of the vector symbols M and H.

This precession is attenuated by the relaxation of angular momentum due to relaxation, and eventually the magnetization is directed in the direction of the magnetic field. Such magnetization motion is represented by the following Landau-Lifshitz-Gilbert (LLG) equation in which a damping term is added to the basic equation of precession motion with the magnetic field direction as the rotation axis.
d ^v M / dt = −γ ^v M × ^v H + (α / M _s ) ^v M × (d ^v M / dt)
Where γ is the magnetorotation ratio, M _s is the saturation magnetization, and α is the Gilbert relaxation constant.

The second term on the right side of the LLG equation represents attenuation, which represents the dissipation of the angular momentum of the spin or magnetic moment. The spin or magnetic moment is aligned in the direction of ^v H after a relaxation time determined for each material, and at that time, the angular momentum of the spin or magnetic moment is dissipated. This dissipation of angular momentum can be extracted outside as a spin current, and this phenomenon is known as spin pumping.

  In recent years, it has been reported that microwave oscillation is caused by passing a spin-polarized current through a CPP (Current Perpendicular to Plane) type GMR element or a TMR (tunnel magnetoresistive) element (for example, Non-patent Document 1, Patent Document). 3 to Patent Document 6).

  FIG. 10 is a conceptual configuration diagram of a conventional CPP type microwave oscillator. A pinned layer 52 made of a ferromagnetic material, a nonmagnetic intermediate layer 53, a free layer 54 made of a ferromagnetic material, and a cap layer on the lower electrode 51. 55 and the upper electrode 56 are provided. When a current is passed through the CPP-type microwave oscillator, a spin-polarized current flows through the free layer 54 due to the filter action of the pinned layer 52, and the spin of this spin-polarized current acts on the magnetization of the free layer 54, causing the magnetization to precess. Microwave oscillation occurs, starting movement.

FIG. 11 is an explanatory diagram of the principle of microwave oscillation by spin torque. When a spin-polarized current or pure spin current is passed through a magnetic material, spin torque is applied to localized spins. This spin torque acts in the opposite direction to the relaxation torque represented by the second term of the above LLG equation to reduce the relaxation torque. as a result,
When a spin-polarized current or pure spin current in an amount satisfying the condition of spin torque> relaxation torque is injected into the magnetic material, the second term of the LLG equation representing the relaxation torque is effectively zero or negative, Spin begins precession and oscillates microwaves.

JP 2002-305337 A JP 2007-059879 A JP 2008-053915 A JP 2007-124340 A JP 2008-071720 A JP 2007-184923 A

S. I. Kiselev et al. , Nature, Vol. 425, pp. 380-383, 2003

  However, conventional CPP type GMR elements and TMR elements require a multilayer film forming process and use a ferromagnetic metal having a large relaxation coefficient α. Therefore, it is necessary to flow a very large current through the ferromagnetic metal, and there is a problem that fine processing for flowing a current through a small area in the direction perpendicular to the surface of the ferromagnetic layer is required. There is also a problem that a sufficient microwave output cannot be obtained as a result of current flowing through a small area in the direction perpendicular to the plane of the ferromagnetic layer.

  In the case of a TMR element, the current flows through the tunnel insulating film, resulting in a high resistance. There is a limit to the flowing current, and the amount of Joule heat generated due to the high resistance increases. There is a problem that becomes unstable.

  Further, in the case of a CPP type GMR element, in order to prevent the magnetization reversal of the free layer due to the spin-polarized current, when trying to increase the output, a plurality of minute current paths are formed in the perpendicular direction of the ferromagnetic layer. Therefore, it is necessary to form fine processing with higher accuracy.

  Therefore, an object of the present invention is to enable microwave oscillation with a simple element structure that does not require a complicated film forming process or fine processing.

  In order to solve the above problems, the present invention is a microwave oscillation device having a junction interface with a metal layer having a spin orbit interaction, and generating a pure spin current from the metal layer to the ferromagnetic layer. Inject to excite microwave oscillation.

  In this way, a current is passed through the metal layer to generate a pure spin current by the spin Hall effect, the generated pure spin current is injected into the ferromagnetic layer, and a relaxation torque is generated in the ferromagnetic layer by the injection of the pure spin current. Microwave oscillation is possible by canceling with torque. In this case, since it has a simple laminated structure of a metal layer and a ferromagnetic layer, a complicated film forming process and fine processing are not required.

  In addition, since the current flows in the in-plane direction, the element size can be freely increased, and the output of microwave oscillation can be easily increased. Furthermore, since the current flows in the in-plane direction, the resistance becomes low, and the injection from the metal layer to the ferromagnetic layer is a pure spin current that does not involve a current unlike the spin-polarized current. Accordingly, no heat is generated, so that the oscillation frequency becomes stable.

  As such a ferromagnetic layer, it is desirable to use a ferromagnetic dielectric layer such as YIG, ferrite oxide, or perovskite Mn oxide having a relaxation coefficient α smaller than that of the metal ferromagnetic material. Since the relaxation coefficient α is small, it is possible to cancel the relaxation torque proportional to α expressed by the second term of the LLG equation with a small current density.

  Further, since no current flows through the ferromagnetic dielectric layer, no heating, chemical change, electromigration, or the like due to the current occurs, so that element degradation can be greatly reduced. In addition, since no Joule heat is generated in the ferromagnetic dielectric layer, the oscillation frequency becomes stable.

Moreover, as a ferromagnetic dielectric layer, YIG (yttrium iron garnet) and yttrium gallium iron garnet which are easily available and have a small relaxation constant α, that is, Y ₃ Fe _5-x Ga _x O ₁₂ ( However, it is desirable to use 0 ≦ x <5).

  As the metal layer, it is desirable to use any of Pt, Au, Pd, Ag, Bi, or an element having an f orbital having a large spin orbit interaction. Since these elements have a large spin-orbit interaction, it is possible to generate a pure spin current by the spin Hall effect with high efficiency and to inject more pure spin current into the ferromagnetic layer. Enables microwave oscillation at threshold current density.

  Since microwave oscillation occurs only by the self-magnetization of the ferromagnetic layer, application of a magnetic field is not indispensable, but the ferromagnetic layer is disposed on the surface of the ferromagnetic layer opposite to the junction interface with the metal layer. A bias layer for biasing the magnetic field direction may be provided. Since the oscillation frequency has a magnetic field strength dependency, the oscillation frequency can be controlled by a bias magnetic field.

  Furthermore, an external magnetic field applying means for applying a variable external magnetic field to the ferromagnetic layer, for example, a wiring for generating bias magnetization, an electromagnet, or the like may be provided. The oscillation frequency can be arbitrarily controlled by changing the external magnetic field generated by such wiring, an electromagnet, or the like.

  Further, a high-output / high-performance microwave oscillation device can be configured by including the above-described microwave oscillation element and an amplifier that amplifies the microwave output from the microwave oscillation element.

  According to the present invention, since only a simple laminated structure of a metal layer and a ferromagnetic layer is required, there is no need for a complicated film forming process and fine processing, and a large output can be achieved.

  In particular, when a ferromagnetic dielectric layer having a small relaxation coefficient α is used as the ferromagnetic layer, it is possible to oscillate at a low threshold current density and to further increase the output.

It is a notional block diagram of the microwave oscillation element of embodiment of this invention. It is explanatory drawing of the spin injection phenomenon in the microwave oscillation element of embodiment of this invention. It is a notional perspective view of the microwave oscillation element of Example 1 of the present invention. It is explanatory drawing of the magnetic field strength dependence of microwave oscillation intensity | strength, and current dependence. It is explanatory drawing of a microwave oscillation threshold current characteristic. It is explanatory drawing of the magnetic field strength dependence of a microwave oscillation frequency. It is a conceptual structure explanatory drawing of the microwave oscillation element of Example 2 of this invention. It is a conceptual structure explanatory drawing of the microwave oscillation element of Example 3 of this invention. It is conceptual structure explanatory drawing of the microwave oscillation apparatus of Example 4 of this invention. It is a conceptual block diagram of the conventional CPP type | mold microwave oscillator. It is explanatory drawing of the microwave oscillation principle by a spin torque.

Here, with reference to FIG.1 and FIG.2, the microwave oscillation element of embodiment of this invention is demonstrated. FIG. 1 is a conceptual configuration diagram of a microwave oscillating device according to an embodiment of the present invention, and includes a laminated structure of a ferromagnetic layer 11 and a metal layer 12 having a spin orbit interaction. The both ends of the metal layer 12 provided terminals 13 _1, 13 _2, the microwave oscillation can be obtained by applying a voltage a current flows in the metal layer 12 by the power source 14.

As the ferromagnetic layer 11 in this case, YIG having a small relaxation coefficient α, that is, Y ₃ Fe _5-x Ga _x O ₁₂ (0 ≦ x <5), ferrite oxide, perovskite Mn oxide, etc. A ferromagnetic dielectric is desirable, but a metal ferromagnetic such as CoFe or CoFeB may also be used.

  Further, the metal layer 12 having a spin orbit interaction may be a single element made of an element having a large spin orbit interaction such as Pt, Au, Pd, Ag, Bi, or an element having an f orbital, or an alloy thereof. Furthermore, these simple substance or alloy may be doped with impurities.

  The thickness of the ferromagnetic layer 11 is such that the thinner the thickness is, the lower the microwave oscillation threshold current density is. Therefore, the thickness for the ferromagnetic layer 11 to exhibit characteristics as a ferromagnetic material is small. For that purpose, a film thickness of about 5 nm is required. Further, when the thickness of the ferromagnetic layer 11 is increased, the microwave oscillation threshold current density is increased, but the microwave oscillation output is increased.

  Moreover, although the thickness of the metal layer 12 is arbitrary, there is an optimum value for each substance for the generation efficiency of the pure spin current by the spin Hall effect, and if it is too thick, the efficiency is deteriorated by the backflow current. Further, if the thickness is too thin, the resistance becomes high, and the amount of Joule heat generated on the metal layer 12 side increases. For example, when Pt is used, a thickness of about 5 to 20 nm is desirable.

  As a method for forming the ferromagnetic layer 11, a plating method or a sputtering method may be used for a metal ferromagnetic material. When a ferromagnetic dielectric is used, any of a liquid phase growth method, a sputtering method, a MOD method (Metal-organic decomposition method), or a sol-gel method may be used. . The crystallinity of the ferromagnetic layer 11 may be single crystal or polycrystal.

  For example, when the MOD method is used, for example, an MOD solution manufactured by Kojundo Chemical Laboratory Co., Ltd. is used and dried on a hot plate heated to 150 ° C. for 5 minutes, so that the excess organic contained in the MOD solution. After evaporating the solvent, the oxide layer is formed by pre-baking in an electric furnace, for example, by heating at 550 ° C. for 5 minutes. Next, in an electric furnace, crystallization of the oxide layer may be advanced in the main firing in which heating is performed at 750 ° C. for 1 to 2 hours to form a YIG layer.

FIG. 2 is an explanatory diagram of the spin injection phenomenon in the microwave oscillation device according to the embodiment of the present invention. As shown in the figure, when a current flows J _c in the metal layer 12, it occurs reverse flow spin-up and spin-down current J _c perpendicular direction by the spin Hall effect, current J _c and the direction perpendicular to the net A spin current J _s is induced and injected into the ferromagnetic layer 11. At this time, the direction of the spin σ of pure spin current J _s is perpendicular to both the current J _c and pure spin current J _c.

Spin torque by pure spin current J _s injected into the ferromagnetic layer 11, the spontaneous magnetization M of the ferromagnetic layer 11 from the time that exceeds the relaxation torque of the second term of the LLG equation stand up the orthogonal direction The precession starts and microwaves are oscillated from the ferromagnetic layer 11. Generating microwave is emitted in a direction perpendicular to the current J _c.

  The generated microwave can be emitted as it is in consideration of the element shape, or can be propagated through the microwave circuit and finally emitted from the antenna.

In this case, since the ferromagnetic layer 11 has a specific magnetization M, microwave oscillation is possible without applying an external magnetic field H. The frequency of the microwave oscillation depends on the saturation magnetization M _s of the material constituting the ferromagnetic layer 11, and when a metallic ferromagnetic material Co is used, an oscillation of several tens of GHz is obtained. When YIG which is a magnetic dielectric is used, oscillation of several GHz can be obtained.

In general, a material having a low saturation magnetization M _s may be selected to reduce the frequency of microwave oscillation, and a material having a large saturation magnetization M _s may be selected to increase the frequency of microwave oscillation. For example, in the case of YIG [Y ₃ Fe _5−x Ga _x O ₁₂ (0 ≦ x <5)], the saturation magnetization M _s decreases as the amount of Fe decreases, so instead of Y ₃ Fe ₅ O ₁₂ By using Y ₃ Fe _5-x Ga _x O ₁₂ (0 <x <5), the oscillation frequency can be reduced.

  Further, as apparent from the second term of the LLG equation, the microwave oscillation threshold current density depends on the relaxation coefficient α. Therefore, the smaller the relaxation coefficient α is, the smaller the oscillation threshold current density is. Is preferably a ferromagnetic dielectric having a small relaxation coefficient α.

Incidentally, the oscillation threshold current density in the conventional CPP type GMR element is 2.2 × 10 ¹¹ A / m ² when the sample size is 130 nm × 70 nm. It became 4 × 10 ⁸ A / m ² , which was 0.2% of the conventional value. Note that when a ferromagnetic dielectric is used, no current flows through the ferromagnetic layer 11, so that heating, chemical change, electromigration, or the like due to current does not occur, and element degradation is greatly reduced. be able to.

  When an external magnetic field H is applied to the microwave oscillating element, the microwave oscillation frequency has a relationship that is substantially proportional to the intensity of the applied external magnetic field H. Therefore, the microwave oscillation frequency can be controlled by applying the external magnetic field H.

  As a means for applying the external magnetic field H, a bias layer made of an antiferromagnetic layer or a ferromagnetic layer may be provided on the surface of the ferromagnetic layer 11 opposite to the joint surface with the metal layer 12, thereby A microwave having a frequency depending on the magnetic field by the bias layer can be obtained.

  Therefore, a plurality of microwave oscillation elements are provided, the magnetization of the bias layer is set so that the magnetic fields applied from the bias layers are different from each other, and a desired microwave oscillation element is arbitrarily selected by the switching element. Thus, a microwave having a frequency of 1 is obtained.

  Alternatively, as in the conventional magnetic field writing type MRAM, a wiring for applying an external magnetic field may be provided in parallel to the ferromagnetic layer 11, and a magnetic field generated with a current may be applied. The microwave oscillation frequency can be made variable by the current flowing through the capacitor.

  Furthermore, it is possible to apply an external magnetic field by arranging permanent magnets or electromagnets at both ends of each microwave oscillating element or microwave oscillating element device. In the case of an electromagnet, the microwave oscillating frequency can be varied. can do.

Based on the above, the microwave oscillating device according to the first embodiment of the present invention will be described next with reference to FIGS. FIG. 3 is a conceptual perspective view of the microwave oscillating device according to the first embodiment of the present invention. Y ₃ Fe ₅ O having a thickness of, for example, 1.5 μm is formed on the GGG single crystal substrate 21 by a liquid phase growth method. _{A 12-component} YIG layer 22 is formed, and a Pt film having a thickness of, for example, 10 nm is deposited thereon by sputtering to form a Pt layer 23. The YIG crystal used in Example 1 was manufactured by FDK Corporation.

Next, after cutting out to a size of 2 mm × 5 mm, the terminals 24 ₁ and 24 ₂ are provided at both ends in the longitudinal direction of the Pt layer 23, thereby completing the basic configuration of the microwave oscillation element of Example 1 of the present invention. Microwave oscillation was observed by applying current to the microwave oscillating element through terminals 24 ₁ and 24 ₂ and applying an external magnetic field H in a direction perpendicular to the current.

  FIG. 4 is an explanatory diagram of the magnetic field intensity dependence and current dependence of the microwave oscillation intensity I. The microwave oscillation intensity I is an intensity when currents are passed in opposite directions to cancel background noise. Difference [I (+ J) −I (−J)]. Complex spikes in the figure indicate that oscillation occurs in many modes due to the shape of the YIG layer 22 and the like. Although not shown here, an output of several tens of pW was obtained when a current of 100 mA was passed.

FIG. 5 is an explanatory diagram of the microwave oscillation threshold current characteristic. In the sample size shown in FIG. 3, the microwave oscillation threshold current was about 40 mA. This value indicates that the spin torque generated by the pure spin current injected into the YIG layer 22 exceeds the relaxation torque by flowing a current of 40 mA through the Pt layer 23. When this is converted into current density, it is about 4.4 × 10 ⁸ A / m ² . Therefore, it was confirmed that the threshold current density was reduced by 3 digits or more as compared with the conventional CPP type GMR element. In addition, S on the vertical axis is a peak-peak value in the current waveform in FIG.

  FIG. 6 is an explanatory diagram of the dependence of the microwave oscillation frequency on the magnetic field strength. When an external magnetic field of 100 mT is applied, microwave oscillation occurs at a frequency of about 5 GHz, and the oscillation frequency is almost equal to the externally applied magnetic field. It was confirmed to be proportional.

Next, with reference to FIG. 7, the microwave oscillation element of Example 2 of this invention is demonstrated. FIG. 7 is a conceptual structural explanatory diagram of the microwave oscillating device according to the second embodiment of the present invention. The microwave oscillating device is composed of a Ta underlayer 33 and IrMn on a silicon substrate 31 through a base insulating film 32 using a mask sputtering method. An antiferromagnetic layer 34, a YIG layer 35, and a Pt layer 36 are sequentially formed, and terminals 37 ₁ and 37 ₂ are provided at both ends of the Pt layer 36. When the antiferromagnetic layer 34 is formed, the antiferromagnetic layer 34 is formed while applying a magnetic field in a direction perpendicular to a line connecting both terminals 37 ₁ and 37 ₂ .

  In the microwave oscillation element of the second embodiment, since the antiferromagnetic layer 34 is a magnetic field bias layer, the microwave oscillation frequency is set to a predetermined value by magnetizing the antiferromagnetic layer 34 to a predetermined intensity in advance. Can be set to a value.

  Next, with reference to FIG. 8, the microwave oscillation element of Example 3 of this invention is demonstrated. FIG. 8 is a conceptual explanatory diagram of a microwave oscillating device according to a third embodiment of the present invention, FIG. 8 (a) is a conceptual side view, and FIG. 8 (b) is an A- It is a conceptual sectional view along an alternate long and short dash line connecting A ′. As shown in the figure, a lower layer wiring 38 is provided on a silicon substrate 31 through a base insulating film 32. Next, the Ta underlayer 33, the YIG layer 35, and the Pt layer 36 are sequentially formed through the interlayer insulating film 39 using a mask sputtering method.

Then, after polishing planarization to expose the surface of the Pt layer 36 is provided an interlayer insulating film 40, the terminal 37 1 on both ends of the Pt layer 36 exposed by using a mask sputtering _method, 37 ₂ provided. Next, an upper layer wiring 42 is formed via the interlayer insulating film 41.

  As shown in FIG. 8C, by flowing currents in opposite directions to the lower layer wiring 38 and the upper layer wiring 42, an external magnetic field directed leftward in the drawing is applied to the YIG layer 35. Therefore, the intensity of the external magnetic field is controlled by controlling the current flowing through the lower layer wiring 38 and the upper layer wiring 42, whereby the microwave oscillation frequency can be made variable.

Next, with reference to FIG. 9, the microwave oscillation apparatus of Example 4 of this invention is demonstrated. Figure 9 is a conceptual configuration diagram of a microwave oscillator according to the fourth embodiment of the present invention, the microwave oscillator _{30 1,} 30 2, · · 30 _n and the amplifier _{43 1,} 43 2, and · · 43 _n Are connected in parallel via a selection circuit 44 to constitute a microwave oscillation device.

In this case, the microwave oscillating elements 30 ₁ , 30 ₂ ,... 30 _{n have} the same configuration as that of the second embodiment, for example, and the microwave oscillating elements 30 ₁ , 30 ₂ ,. The magnitude of magnetization of the bias layer constituting 30 _n is set to be different for each element. Therefore, it is possible to oscillate microwaves of a desired frequency by switching the microwave oscillator _{30 1, 30 2, ·· 30} n to flow a current by the selection circuit 44.

The microwave is amplified by an amplifier 43 _i connected to the microwave oscillating element 30 _i and is emitted from the antenna through a predetermined microwave circuit (not shown).

  Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the configurations and conditions described in the embodiments and examples, and various modifications can be made. For example, in each of the above embodiments, Pt is used as the metal layer. However, the metal layer is not limited to Pt. Like Pt, Pd, Au, Ag, Bi, and the like having a large spin-orbit interaction are used. An element having an f orbit may be used. Furthermore, it is not necessary to be a single metal, and these alloys may be used, and further, those obtained by adding impurities to these single metals or alloys may be used.

  In Example 2 or Example 4 described above, an antiferromagnetic layer such as IrMn is provided in the YIG layer to bias the magnetization direction, but a metal ferromagnetic material such as CoFeB may be used.

In each of the above embodiments, Y ₃ Fe _5-x Ga _x O ₁₂ (where 0 ≦ x <5) is used as the ferromagnetic dielectric, but pure Y ₃ Fe _5-x Ga is used. It is not limited to _x O _12, or may be doped with impurities such as Bi and Si. Furthermore, a ferromagnetic dielectric other than Y ₃ Fe _5-x Ga _x O ₁₂ may be used.

  In the third embodiment, two lines for generating the bias magnetic field are provided on the upper and lower sides, but either one may be used.

11 Ferromagnetic layer 12 Metal layer 13 ₁ , 13 ₂ terminal 14 Power supply 21 GGG single crystal substrate 22 YIG layer 23 Pt layer 24 ₁ , 24 ₂ terminal 30 _i microwave oscillation element 31 Silicon substrate 32 Base insulating film 33 Ta base layer 34 antiferromagnetic layer 35 YIG layer 36 Pt layer 37 ₁ , 37 ₂ terminal 38 lower layer wiring 39 interlayer insulating film 40 interlayer insulating film 41 interlayer insulating film 42 upper layer wiring 43 _i amplifier 44 selection circuit 51 lower electrode 52 pinned layer 53 nonmagnetic Intermediate layer 54 Free layer 55 Cap layer 56 Upper electrode

Claims (7)

  A microwave oscillation element having a junction interface between a ferromagnetic layer and a metal layer having a spin orbit interaction, and injecting a pure spin current from the metal layer into the ferromagnetic layer to excite microwave oscillation.   The microwave oscillation element according to claim 1, wherein the ferromagnetic layer is made of a ferromagnetic dielectric layer. The microwave oscillation element according to claim 2, wherein the ferromagnetic dielectric layer is made of Y ₃ Fe _5−x Ga _x O ₁₂ (where 0 ≦ x <5).   The metal layer having the spin orbit interaction is a metal layer made of any one of elements having Pt, Au, Pd, Ag, Bi, or f orbit. The microwave oscillation element of description. 5. The bias layer for biasing a magnetic field direction to the ferromagnetic layer is provided on a surface of the ferromagnetic layer opposite to a bonding interface with the metal layer. 6. Microwave oscillation element. The microwave oscillation element according to claim 1, further comprising an external magnetic field applying unit that applies a variable external magnetic field to the ferromagnetic layer. A microwave oscillation device comprising: the microwave oscillation element according to any one of claims 1 to 6; and an amplifier that amplifies a microwave output from the microwave oscillation element.

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