CN107895624B - Multilayer film with enhanced optical mode ferromagnetic resonance - Google Patents
Multilayer film with enhanced optical mode ferromagnetic resonance Download PDFInfo
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- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/32—Spin-exchange-coupled multilayers, e.g. nanostructured superlattices
- H01F10/324—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer
- H01F10/3268—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer the exchange coupling being asymmetric, e.g. by use of additional pinning, by using antiferromagnetic or ferromagnetic coupling interface, i.e. so-called spin-valve [SV] structure, e.g. NiFe/Cu/NiFe/FeMn
- H01F10/3272—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer the exchange coupling being asymmetric, e.g. by use of additional pinning, by using antiferromagnetic or ferromagnetic coupling interface, i.e. so-called spin-valve [SV] structure, e.g. NiFe/Cu/NiFe/FeMn by use of anti-parallel coupled [APC] ferromagnetic layers, e.g. artificial ferrimagnets [AFI], artificial [AAF] or synthetic [SAF] anti-ferromagnets
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- H01F41/14—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates
- H01F41/18—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates by cathode sputtering
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Abstract
The embodiment of the invention discloses an optical mode ferromagnetic resonance enhanced multilayer film, which comprises a first uniaxial magnetic anisotropic layer, a nonmagnetic isolating layer and a second uniaxial magnetic anisotropic layer, wherein the directions of easy magnetization axes of the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer are consistent, and the thickness of the nonmagnetic isolating layer is configured to enable the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer to be antiferromagnetically coupled. In the multilayer film with enhanced optical mode ferromagnetic resonance provided by the embodiment of the invention, two single-axis magnetic anisotropic layers can still keep ferromagnetic resonance with smaller magnetic loss along an internal magnetic anisotropic field under a zero bias magnetic field; in addition, due to the interlayer antiferromagnetic coupling effect, on one hand, the magnetic moments of the two uniaxial magnetic anisotropic layers with the same easy magnetization axis direction precess along effective magnetic fields in opposite directions respectively; on the other hand, the optical mode resonance frequency and the magnetic permeability of the ferromagnetic resonance multilayer film are greatly improved.
Description
Technical Field
The invention relates to the technical field of soft magnetic thin film materials, in particular to a multilayer film with enhanced optical mode ferromagnetic resonance.
Background
Ferromagnetic resonance is a phenomenon that ferromagnetic substances generate strong absorption resonance in a certain external constant magnetic field and a microwave magnetic field with certain frequency when certain conditions are met, belongs to a basic physical phenomenon of microwave soft magnetic materials, and various microwave devices made by utilizing the ferromagnetic resonance phenomenon are widely applied in the fields of communication, information, aerospace, military and the like.
The upper limit frequency of the microwave device is determined by the ferromagnetic resonance frequency of the microwave soft magnetic material, and along with the development of science and technology, the upper limit frequency of the microwave device is required to be higher and higher, and correspondingly, the ferromagnetic resonance frequency of the microwave soft magnetic material is also required to be higher and higher.
The resonant frequencies of the microwave soft magnetic material mainly include an acoustic mode resonant frequency and an optical mode resonant frequency. In the prior art, the acoustic mode resonance frequency of a microwave soft magnetic material is better applied to a microwave device, but at present, the higher ferromagnetic resonance frequency is more and more difficult to obtain by improving the acoustic mode resonance frequency; in multilayer film systems, the optical mode resonance frequency is generally higher than that of the acoustic mode, but the optical mode has not been put to practical use because of its low permeability. Therefore, how to improve the magnetic permeability to a practical level while taking advantage of the high ferromagnetic resonance frequency characteristics of the optical mode is a problem to be solved.
Disclosure of Invention
The embodiment of the invention provides an optical mode ferromagnetic resonance enhanced multilayer film, which is based on optical mode ferromagnetic resonance and is used for solving the problems of improving the ferromagnetic resonance frequency and the magnetic conductivity of a microwave soft magnetic material in the prior art.
In order to solve the technical problem, the embodiment of the invention discloses the following technical scheme:
an optical mode ferromagnetic resonance enhanced multilayer film comprising a first uniaxial magnetic anisotropic layer, a nonmagnetic spacer layer and a second uniaxial magnetic anisotropic layer, the nonmagnetic spacer layer being sandwiched between the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer, the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer having a magnetization easy axis direction which is coincident, the nonmagnetic spacer layer having a thickness configured to antiferromagnetically couple the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer.
Preferably, the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer have the same thickness.
Preferably, the first uniaxial magnetic anisotropic layer and/or the second uniaxial magnetic anisotropic layer has a thickness of
Preferably, the first uniaxial magnetic anisotropic layer and/or the second uniaxial magnetic anisotropic layer comprise a ferromagnetic element and a doping element, the ferromagnetic element is uniformly distributed, and the doping element is distributed in a gradient manner along one direction.
Preferably, the ferromagnetic element comprises one or a combination of more than one of Fe, Ni, Co.
Preferably, the doping element includes a combination element of a non-metal element, a metal element and/or an oxide.
Preferably, the non-metal element in the doping elements comprises B, C, N, O, Si; the metal element in the doping elements comprises one or more of Hf, Zr, Al, Nb, Ta, Ru, V, Mo, W and Cr; the oxide of the doping element comprises Al2O3、MgO、ZrO2、ZnO、HfO2、SiO2、TiO2、Ta2O5、V2O5、Nd2O3、Cr2O3、(Ba,Sr)TiO3One or a combination of more than one of them.
Preferably, the nonmagnetic spacer layer comprises a metal and/or an oxide.
Preferably, the metal in the nonmagnetic isolating layer comprises one or more of Ru, Ta, Au, Hf, Cr and Nb; the oxide in the nonmagnetic spacer layer comprises Al2O3、MgO、SiO2One or a combination of more than one of them.
A method for preparing an optical mode ferromagnetic resonance enhanced multilayer film by using a vacuum magnetron sputtering apparatus, the method comprising:
step S100: sputtering a first uniaxial magnetic anisotropic layer on a substrate;
step S200: uniformly sputtering a non-magnetic isolation layer with a certain thickness on the first uniaxial magnetic anisotropic layer;
step S300: sputtering a second uniaxial magnetic anisotropic layer in accordance with the direction of the easy magnetization axis of the first uniaxial magnetic anisotropic layer on the nonmagnetic spacer layer, and configuring the thickness of the nonmagnetic spacer layer so that antiferromagnetic coupling is satisfied between the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer.
According to the technical scheme, the uniaxial magnetic anisotropy of the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer in the multilayer film with enhanced optical mode ferromagnetic resonance provided by the embodiment of the invention ensures that the two uniaxial magnetic anisotropic layers can still keep ferromagnetic resonance with smaller magnetic loss along the internal magnetic anisotropic field under the zero-bias magnetic field; in addition, due to the anti-ferromagnetic coupling effect of the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer, on one hand, the magnetic moments of the two uniaxial magnetic anisotropic layers with the same easy magnetization axis direction respectively precess along effective magnetic fields in opposite directions, so that the positive superposition of the optical mode ferromagnetic resonance amplitudes of the two uniaxial magnetic anisotropic layers with opposite phases is enhanced, and the magnetic conductivity is improved; on the other hand, a strong antiferromagnetic coupling field is applied to the precessing magnetic moment, so that the optical mode resonance frequency of the ferromagnetically resonant multilayer film is greatly increased.
Drawings
In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a first multilayer film structure with enhanced optical mode ferromagnetic resonance provided in an embodiment of the present invention;
FIG. 2 is a schematic diagram of a second multilayer film structure with enhanced optical mode ferromagnetic resonance provided in an embodiment of the present invention;
FIG. 3 is a schematic diagram of an optical mode stack in an optical mode ferromagnetic resonance enhanced multilayer film according to an embodiment of the present invention;
FIG. 4 is a top view of the optical mode stack of FIG. 3;
FIG. 5 is a schematic diagram illustrating superposition of acoustic modes in an optical mode ferroresonance enhanced multilayer film according to an embodiment of the present invention;
FIG. 6 is a top view of the acoustic mode stacking diagram of FIG. 4;
FIG. 7 is a schematic flow chart of a method for preparing an optical mode ferromagnetic resonance enhanced multilayer film according to an embodiment of the present invention;
FIG. 8 is a schematic view of sputtering of a uniaxial magnetic anisotropic layer in an embodiment of the invention;
FIG. 9 is a schematic diagram illustrating the sputtering of a non-magnetic spacer layer according to an embodiment of the present invention;
the symbols in fig. 1-9 are represented as: 1-first uniaxial magnetic anisotropic layer, 2-nonmagnetic spacer layer, 3-second uniaxial magnetic anisotropic layer, 4-circular turntable, 51-ferromagnetic mother material target, 52-doping element target, 53-nonmagnetic spacer layer sputtering target, 6-substrate.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to develop and utilize the optical mode resonance frequency and the magnetic permeability of the microwave soft magnetic material and enable the optical mode resonance frequency and the magnetic permeability to reach the practical degree, the embodiment of the invention provides the multilayer film with the enhanced optical mode ferromagnetic resonance. Fig. 1 is a first schematic diagram of a multilayer film structure with enhanced optical mode ferromagnetic resonance provided in an embodiment of the present invention, and fig. 2 is a second schematic diagram of a multilayer film structure with enhanced optical mode ferromagnetic resonance provided in an embodiment of the present invention, as shown in fig. 1 in combination with fig. 2, the multilayer film with enhanced optical mode ferromagnetic resonance provided in an embodiment of the present invention includes a first uniaxial magnetic anisotropic layer 1, a nonmagnetic spacer layer 2, and a second uniaxial magnetic anisotropic layer 3, the nonmagnetic spacer layer 2 is sandwiched between the first uniaxial magnetic anisotropic layer 1 and the second uniaxial magnetic anisotropic layer 3, and the directions of easy magnetization axes of the first uniaxial magnetic anisotropic layer 1 and the second uniaxial magnetic anisotropic layer 3 are the same (the directions are indicated by arrows in fig. 1), and the orientations of magnetic moments are opposite (the directions are indicated by arrows in fig. 2). The uniaxial magnetic anisotropy of the first uniaxial magnetic anisotropic layer 1 and the second uniaxial magnetic anisotropic layer 3 ensures that the two uniaxial magnetic anisotropic layers can still keep ferromagnetic resonance with smaller magnetic loss along the generated magnetic anisotropic field under a zero magnetic field.
In addition, the nonmagnetic spacer layer 2 is controlled to an appropriate thickness so that the first uniaxial magnetic anisotropic layer 1 and the second uniaxial magnetic anisotropic layer 3 are antiferromagnetically coupled to each other. In an embodiment of the invention, the thickness of the non-magnetic spacer layer 2 is chosen
Can satisfy any thickness of the condition that the first uniaxial magnetic anisotropic layer 1 and the second uniaxial magnetic anisotropic layer 3 are mutually antiferromagnetic-coupled. That is, the thickness of the nonmagnetic spacer layer 2 can be selected within the range according to actual needs by those skilled in the art, for example,
orEtc. as long as the thickness is such that the first uniaxial magnetic anisotropic layer 1 and the second uniaxial magnetic anisotropic layer 3 are antiferromagnetically coupled, it should fall within the scope of the present invention. Since the thickness of the nonmagnetic spacer layer 2 is related to the material and thickness of the first uniaxial magnetic anisotropic layer 1 and the second uniaxial magnetic anisotropic layer 3, a uniform value cannot be given, but the antiferromagnetic coupling condition can be determined by hysteresis loop measurement.
In the embodiment of the invention, the antiferromagnetic coupling effect of the first uniaxial magnetic anisotropic layer 1 and the second uniaxial magnetic anisotropic layer 3 makes the magnetic moments of the two uniaxial magnetic anisotropic layers with the same easy magnetization axis direction precess along the effective magnetic fields in opposite directions respectively, so that the positive superposition of the optical mode ferromagnetic resonance amplitudes of the two uniaxial magnetic anisotropic layers with opposite phases is enhanced, and the magnetic permeability is improved; on the other hand, a strong antiferromagnetic coupling field is applied to the precessing magnetic moment, so that the optical mode resonance frequency of the ferromagnetic resonance multilayer film is greatly improved, and the optical mode of the microwave soft magnetic material is practical.
In order to facilitate those skilled in the art to better understand the mechanism of the optical mode resonance frequency and magnetic permeability enhancement and the acoustic mode resonance reduction in the multilayer film with optical mode ferromagnetic resonance enhancement provided by the embodiments of the present invention, the following detailed description is provided with reference to the accompanying drawings.
FIG. 3 is a schematic diagram of stacking optical modes in an optical mode ferromagnetic resonance enhanced multilayer film according to an embodiment of the present invention, where M in FIG. 31And M2Respectively, the magnetic moments of the first and second uniaxial magnetic anisotropic layers 1 and 3, m1And m2Each represents M1And M2In a microwave alternating field HacProjection in the direction HKRepresenting a uniaxial magnetic anisotropy field, JeffRepresenting the interlayer antiferromagnetic coupling field, and Hac is the microwave field applied at ferromagnetic resonance.
Interlayer antiferromagnetic coupling of the first uniaxial magnetic anisotropic layer 1 and the second uniaxial magnetic anisotropic layer 3 causes the magnetic moment M1And M2Along the effective field H of the magnetic fieldeff(Heff＝HK+Jeff) Moving in the opposite direction. FIG. 4 is a top view of the optical mode stack of FIG. 3, showing the magnetic moment M in FIG. 41And M2Along the effective magnetic field HeffThe positive precession in the opposite direction enhances the positive superposition of the resonant amplitudes of the optical modes in opposite phase (opposite precession direction), thereby increasing the permeability. Wherein the optical mode resonance amplitude is in the microwave alternating field HacUpper sum amplitude mac＝2mcosωt，m＝m1＝m2. In addition, a strong antiferromagnetic coupling field JeffApplied to precessing magnetic moments of two uniaxial magnetic anisotropic layersThe resonant frequency of the optical mode is greatly improved.
Fig. 5 is a schematic diagram of superposition of acoustic modes in a multilayer film with enhanced optical mode ferromagnetic resonance provided by an embodiment of the present invention, and fig. 6 is a top view of the schematic diagram of superposition of acoustic modes in fig. 5, as shown in fig. 5 in combination with fig. 6, a magnetic moment M1And M2Along the effective magnetic field HKMoving in opposite directions just cancels out the acoustic mode resonances in phase (same direction of precession). Wherein the resonance frequency of the acoustic mode is in the microwave alternating field HacAmplitude in direction is constantly zero, mac≡0。
Therefore, the anti-ferromagnetic coupling multilayer film system composed of the uniaxial magnetic anisotropic layer and the non-magnetic isolation layer 2 realizes optical mode resonance enhancement and acoustic mode resonance cancellation, so that the optical mode resonance frequency of the anti-ferromagnetic coupling multilayer film system is greatly improved by more than 2 times compared with that of a single-layer ferromagnetic film, the ferromagnetic resonance frequency is higher than 10GHz under the condition of no external bias magnetic field, and the optical mode magnetic permeability is higher than 10-30 and far higher than that of a common multilayer film; the magnetic anisotropy antiferromagnetic coupling multilayer film prepared by the invention is proved to have reached the practical degree in the microwave material application.
The multilayer film with the enhanced optical mode ferromagnetic resonance provided by the embodiment of the invention is mainly applied to microwave devices, and needs two uniaxial magnetic anisotropic layers with certain thickness, otherwise, because the total magnetic moment is too small, the magnetic influence of the microwave devices is too small, and the application value is lost. However, due to the limitation of the exchange coupling action distance between the magnetic multilayer film layers, the two uniaxial magnetic anisotropic layers cannot be too thick, so that the thickness value of the two uniaxial magnetic anisotropic layers has a reasonable range. Specifically, the two uniaxial magnetic anisotropic layers cannot be too thin, on one hand, because the microwave device has a requirement on large magnetic moment, and on the other hand, because the two uniaxial magnetic anisotropic layers are too thin, interlayer antiferromagnetic coupling is difficult to realize; the two ferromagnetic layers cannot be too thick either because the strength of the interlayer coupling of the two ferromagnetic films separated by the nonmagnetic layer is not only influenced by the thickness of the nonmagnetic layer (the thinner the coupling strength is greater) but also related to the thickness of the ferromagnetic films. Under the condition that the thickness of the nonmagnetic isolating layer is certain, a thickness maximum value exists between the thicknesses of the two ferromagnetic layers, when the thickness of the two ferromagnetic layers exceeds the thickness maximum value, the interlayer coupling effect of the film at the exceeding part is very weak, the ferromagnetic coupling component is increased on the basis of the original antiferromagnetic coupling, and therefore the relative strength of optical mode resonance is weakened, and adverse effects are brought.
Based on the above-mentioned factors, in a preferred embodiment of the present invention, the lower limit and the upper limit of the thickness of the two uniaxial magnetic anisotropic layers are set to
And
i.e. the selection of the thicknesses of the first and second uniaxial magnetic anisotropic layers 1 and 3
Any one of the above values, for example,or
And the like. In order to ensure that the spin currents emitted by the first uniaxial magnetic anisotropic layer 1 and the second uniaxial magnetic anisotropic layer 3 during ferromagnetic resonance cancel each other, the thicknesses of the spin currents are the same, so that extra loss caused by emission of the spin currents is reduced.
In a preferred embodiment of the present invention, the first uniaxial magnetic anisotropic layer 1 and/or the second uniaxial magnetic anisotropic layer 3 include a ferromagnetic element and a doping element. The ferromagnetic elements are uniformly distributed, the doping elements are distributed in a gradient manner along one direction, and the gradient distribution of the doping elements causes the uniaxial magnetic anisotropy of the ferromagnetic thin film, namely, the magnetization easy axis direction of the first uniaxial magnetic anisotropic layer 1 and the second uniaxial magnetic anisotropic layer 3 is determined by the gradient distribution direction of the doping elements.
In addition, the ferromagnetic element can be one or more of Fe, Ni and Co; the doping elements can be selected from non-metallic elements,A combination of metal elements and/or oxides. Wherein, the non-metal element in the doping element can be one or the combination of more than one of B, C, N, O and Si; the metal element in the doping element can be one or the combination of more than one of Hf, Zr, Al, Nb, Ta, Ru, V, Mo, W and Cr; the oxide comprises Al2O3、MgO、ZrO2、ZnO、HfO2、SiO2、TiO2、Ta2O5、V2O5、Nd2O3、Cr2O3And (Ba, Sr) TiO3One or a combination of more than one of them. The atomic ratio of the ferromagnetic element and the doping element can be adjusted by those skilled in the art according to actual needs, for example, the atomic percentage of the ferromagnetic element is controlled to 55-98%, and correspondingly, the atomic percentage of the doping element is controlled to 2-45%.
In a preferred embodiment of the invention, the non-magnetic separation layer 2 may be chosen from metals and/or oxides. Wherein, the metal in the nonmagnetic isolating layer 2 can be one or the combination of more than one of Ru, Ta, Au, Hf, Cr and Nb; the oxide in the non-magnetic isolating layer 2 can be selected from Al2O3、MgO、SiO2And (Ba, Sr) TiO3One or a combination of more than one of them.
It should be noted that the elemental composition of each layer in the optical mode ferromagnetic resonance enhanced multilayer film is only a part of specific elements or oxides listed in the embodiments of the present invention, but the elements and oxides in nature are various and cannot be exhaustive in the embodiments of the present invention, and any combination of elements and/or oxides that can satisfy the above properties should fall within the scope of the present invention.
In addition, the above description only exemplifies the arrangement of the uniaxial magnetic anisotropic layer (uniform distribution of ferromagnetic elements, gradient distribution of doping elements), and the implementation of the antiferromagnetic coupling between the two uniaxial magnetic anisotropic layers (by setting the thickness of the nonmagnetic spacer layer), but it should be understood that those skilled in the art can also adopt other ways to prepare the uniaxial magnetic anisotropic layer and implement the antiferromagnetic coupling between the two uniaxial magnetic anisotropic layers, and the present invention is not particularly limited thereto, that is, all three-layer film structures having the first uniaxial magnetic anisotropic layer, the nonmagnetic spacer layer, and the second uniaxial magnetic anisotropic layer satisfy the condition: the easy magnetization axes of the two uniaxial magnetic anisotropic layers are consistent; it is intended that both of the uniaxial magnetic anisotropic layers be antiferromagnetically coupled and fall within the scope of the present invention.
In view of the above multilayer film with enhanced optical mode ferromagnetic resonance, an embodiment of the present invention further provides a method for preparing a multilayer film with enhanced optical mode ferromagnetic resonance, which uses a vacuum magnetron sputtering apparatus, as shown in fig. 7, and the method includes the following steps:
step S100: sputtering a first uniaxial magnetic anisotropic layer 1 on a substrate 6;
fig. 8 is a schematic diagram of sputtering of a uniaxial magnetic anisotropic layer in an embodiment of the invention, as shown in fig. 8, a substrate 6 is attached to a circular turntable 4, a ferromagnetic mother material target 51 (the ferromagnetic mother material target 51 is used for sputtering a ferromagnetic element) is arranged, the ferromagnetic mother material target 51 and the substrate 6 are parallel, and the center of the ferromagnetic mother material target 51 is opposite to the center of the substrate 6, so that the ferromagnetic element sputtered by the ferromagnetic mother material target 51 is uniformly sputtered on the substrate 6 when the circular turntable 4 drives the substrate 6 to rotate at a constant speed; arranging a doping element target 52 (the doping element target 52 is used for sputtering doping elements), enabling the center of the doping element target 52 to deviate from the center of the substrate 6 by 4-10cm in the direction away from the center of the circular turntable 4, adjusting the inclination angle of the doping element target 52, and enabling the central axis of the doping element target 52 to be aligned with the outer side of the substrate 6, so that when the circular turntable 4 drives the substrate 6 to rotate at a constant speed, the doping elements sputtered by the doping element target 52 are distributed on the substrate 6 in a gradient manner along the direction L in the figure 6.
In a preferred embodiment, to distinguish the anisotropy direction of the multilayer film with enhanced optical mode ferroresonance, a strip-shaped substrate is selected, the strip-shaped substrate is attached to the edge of the circular turntable 4, and the length direction of the strip-shaped substrate is arranged along the radial direction of the circular turntable 4, i.e. the direction L in fig. 8 is the length direction of the strip-shaped substrate.
Under vacuum magnetic control sputteringThe vacuum pressure of the vacuum cavity of the injection device is lower than 5.0 multiplied by 10－6After the Torr is carried out, introducing Ar gas, wherein the flow rate is 20sccm, and the pressure of sputtering working gas is 2.8 mTorr; the sputtering power and sputtering time were set to obtain the first uniaxial magnetic anisotropic layer 1 of the corresponding thickness. Wherein, the corresponding sputtering power is selected according to the materials of the ferromagnetic parent material target 51 and the doping element target 52; the corresponding sputtering time is selected according to the thickness of the uniaxial magnetic anisotropic layer (the longer the sputtering time, the thicker the thickness of the uniaxial magnetic anisotropic layer).
For example, when the ferromagnetic master material target 51 is Fe0.5Co0.5When the target is a B target, the target is co-sputtered under the conditions that the sputtering power is respectively 80W and 120W, the sputtering time is 30min, and the target can be plated
A thick FeCoB ferromagnetic film;
when the ferromagnetic parent material target 51 is Fe0.7Co0.3When the target is a B target, the target is co-sputtered at sputtering power of 80W and 150W for 800s to obtain a target
A thick FeCoB ferromagnetic film;
when the ferromagnetic parent material target 51 is Fe0.5Co0.5Target, doping element target 52 is Al2O3When the target is used, the target is co-sputtered under the conditions that the sputtering power is respectively 80W and 120W, and the sputtering time is 880s, and the target can be platedThick (Fe)0.5Co0.5)x(Al2O3)yA ferromagnetic thin film;
when the ferromagnetic parent material target 51 is Fe0.7Co0.3When the target is Hf target, the doping element target 52 is co-sputtered at 80W and 60W for 1000s
Thick (Fe)0.7Co0.3)xHfyA ferromagnetic thin film.
Step S200: uniformly sputtering a non-magnetic isolating layer 2 with a certain thickness on the first uniaxial magnetic anisotropic layer 1;
fig. 9 is a schematic diagram of the sputtering of the nonmagnetic spacer layer 2 in the embodiment of the present invention, and as shown in fig. 9, the nonmagnetic spacer layer sputtering target 53 is disposed such that the nonmagnetic spacer layer sputtering target 53 is parallel to the substrate 6, and the center of the nonmagnetic spacer layer sputtering target 53 is opposite to the center of the substrate 6, so that when the circular turntable 4 drives the substrate 6 to rotate at a constant speed, the nonmagnetic spacer layer 2 sputtered by the nonmagnetic spacer layer sputtering target 53 is uniformly sputtered on the first uniaxial magnetic anisotropic layer 1.
The vacuum pressure in the vacuum cavity of the vacuum magnetron sputtering device is lower than 5.0 multiplied by 10－6After the Torr is carried out, introducing Ar gas, wherein the flow rate is 20sccm, and the pressure of sputtering working gas is 2.8 mTorr; the sputtering power and the sputtering time are set to obtain a thickness of
The non-magnetic spacer layer 2.
For example, when the nonmagnetic spacer sputtering target 53 is a Ru target, sputtering is carried out at a sputtering power of 30W for a sputtering time of 30min, and plating can be carried outA thick Ru nonmagnetic spacer layer 2;
when the non-magnetic separation layer sputtering target 53 is Ru target, sputtering is carried out under the condition that the sputtering power is 30W, the sputtering time is 1min, and the plating can be obtained
A thick Ru nonmagnetic spacer layer 2;
when the non-magnetic isolation layer sputtering target 53 is Au target, sputtering is carried out under the condition that the sputtering power is 20W, the sputtering time is 1min, and the plating can be obtained
A thick Au nonmagnetic spacer layer 2;
when the non-magnetic isolation layer sputtering target 53 is MgO target, sputtering is carried out under the condition of sputtering power of 100W, the sputtering time is 10min, and the plating can be obtained
A thick MgO non-magnetic separation layer 2.
Step S300: a second uniaxial magnetic anisotropic layer 3 in accordance with the direction of the easy magnetization axis of the first uniaxial magnetic anisotropic layer 1 is sputtered on the nonmagnetic spacer layer 2, and the thickness of the nonmagnetic spacer layer 2 is configured so that antiferromagnetic coupling is satisfied between the first uniaxial magnetic anisotropic layer 1 and the second uniaxial magnetic anisotropic layer 2.
In the present step, the second uniaxial magnetic anisotropic layer 3 is sputtered on the nonmagnetic spacer layer 2 in the same manner as in step S100, wherein the dopant element target 52 is provided in the same manner as in step S100 in order to ensure that the magnetization easy axes of the first uniaxial magnetic anisotropic layer 1 and the second uniaxial magnetic anisotropic layer 3 are aligned. In addition, the step S100 can be referred to for the arrangement of the ferromagnetic mother material target 51 and the sputtering condition, and the description thereof is omitted for brevity.
The multilayer film with the enhanced optical mode ferromagnetic resonance can be obtained by adopting the method according to different sputtering targets and sputtering conditions. For example, each thickness is
And
of (Fe)0.7Co0.3)xBy/Ru/(Fe0.7Co0.3)xByMultilayer film, under zero magnetic field, it only shows optical mode ferromagnetic resonance, the resonant frequency is up to 12GHz, and the magnetic permeability is up to 15 too; each thickness is
And
of (Fe)0.5Co0.5)x(Al2O3)y/Au/(Fe0.5Co0.5)x(Al2O3)yMultilayer film, under zero magnetic field, it only shows optical mode ferromagnetic resonance, the resonant frequency is as high as 10.8GHz, and the magnetic permeability is as high as 21; each thickness is
And
of (Fe)0.7Co0.3)xHfy/MgO/(Fe0.7Co0.3)xHfyThe multilayer film only shows optical mode ferromagnetic resonance under zero magnetic field, the resonance frequency is as high as 9.8GHz, and the magnetic permeability is also as high as 30.
The foregoing are several exemplary multilayer films with enhanced optical mode ferroresonance prepared by the method for preparing a multilayer film with enhanced optical mode ferroresonance provided in the embodiments of the present invention, but it should be noted that the multilayer film with enhanced optical mode ferroresonance prepared by the method is not limited thereto, and those skilled in the art can adjust the sputtering target and sputtering conditions accordingly according to actual needs to obtain corresponding multilayer films with enhanced optical mode ferroresonance, which all fall within the protection scope of the present invention.
According to the technical scheme, the uniaxial magnetic anisotropy of the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer in the multilayer film with enhanced optical mode ferromagnetic resonance provided by the embodiment of the invention ensures that the two uniaxial magnetic anisotropic layers can still keep ferromagnetic resonance with smaller magnetic loss along the internal magnetic anisotropic field under the zero-bias magnetic field; in addition, due to the anti-ferromagnetic coupling effect of the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer, on one hand, the magnetic moments of the two uniaxial magnetic anisotropic layers with the same easy magnetization axis direction respectively precess along effective magnetic fields in opposite directions, so that the positive superposition of the optical mode ferromagnetic resonance amplitudes of the two uniaxial magnetic anisotropic layers with opposite phases is enhanced, and the magnetic conductivity is improved; on the other hand, a strong antiferromagnetic coupling field is applied to the precessing magnetic moment, so that the optical mode resonance frequency of the ferromagnetically resonant multilayer film is greatly increased.
It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The foregoing are merely exemplary embodiments of the present invention, which enable those skilled in the art to understand or practice the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. An optical mode ferromagnetic resonance enhanced multilayer film comprising a first uniaxial magnetic anisotropic layer, a nonmagnetic spacer layer and a second uniaxial magnetic anisotropic layer, the nonmagnetic spacer layer being sandwiched between the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer, the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer having a uniform direction of easy magnetization axis and opposite orientations of magnetic moments, the nonmagnetic spacer layer having a thickness configured to antiferromagnetically couple the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer;
wherein the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer have the same thickness, and the nonmagnetic spacer layer has a thickness of
Any thickness satisfying the condition that the first uniaxial magnetic anisotropic layer and the second uniaxial magnetic anisotropic layer are mutually antiferromagnetically coupled.
2. An optical mode ferroresonance enhanced multilayer film according to claim 1, wherein the thickness of the first uniaxial magnetic anisotropic layer and/or the second uniaxial magnetic anisotropic layer is/are
3. An optical mode ferroresonance enhanced multilayer film according to claim 1 or 2, wherein the first uniaxial magnetic anisotropic layer and/or the second uniaxial magnetic anisotropic layer comprises a ferromagnetic element in a uniform distribution and a doping element in a gradient distribution along the easy axis direction;
wherein the doping element comprises a combination element of a nonmetal element, a metal element and/or an oxide.
4. An optical mode ferroresonance enhanced multilayer film in accordance with claim 3, wherein said ferromagnetic element comprises one or a combination of more than one of Fe, Ni, Co.
5. An optical mode ferroresonance enhanced multilayer film as in claim 3, wherein said non-metallic element of doping elements comprises one or more of B, C, N, O, SiCombinations of the above; the metal element in the doping elements comprises one or more of Hf, Zr, Al, Nb, Ta, Ru, V, Mo, W and Cr; the oxide of the doping element comprises Al2O3、MgO、ZrO2、ZnO、HfO2、SiO2、TiO2、Ta2O5、V2O5、Nd2O3、Cr2O3、(Ba,Sr)TiO3One or a combination of more than one of them.
6. An optical mode ferroresonance enhanced multilayer film according to claim 1 or 2, wherein the nonmagnetic spacer layer comprises a metal and/or an oxide.
7. An optical mode ferroresonance enhanced multilayer film in accordance with claim 6, wherein the metal in the nonmagnetic spacer layer comprises one or a combination of more than one of Ru, Ta, Au, Hf, Cr, Nb; the oxide in the nonmagnetic spacer layer comprises Al2O3、MgO、SiO2One or a combination of more than one of them.
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