Nowadays the yttrium iron garnet(Y3Fe5O12, YIG) films are widely used in the microwave and spin wave devices due to their low damping constant and long propagation distance for spin waves. However, the performances, e...Nowadays the yttrium iron garnet(Y3Fe5O12, YIG) films are widely used in the microwave and spin wave devices due to their low damping constant and long propagation distance for spin waves. However, the performances, especially the frequency stability, are seriously affected by the relaxation of the interface magnetic moments. In this study, the effect of out-of-plane magnetization depinning on the resonance frequency shift(△ fr) was investigated for 3-μm YIG films grown on Gd3Ga5O12(GGG)(111) substrates by liquid-phase epitaxy. It is revealed that the ferromagnetic resonance(FMR) and spin wave propagation exhibit a very slow relaxation with relaxation time τ even longer than one hour under an out-of-plane external magnetic bias field. The △ fr span of 15.15–24.70 MHz is observed in out-of-plane FMR and forward volume spin waves. Moreover, the △ fr and τ depend on the magnetic field. The △ fr can be attributed to that the magnetic moments break away from the pinning layer at the YIG/GGG interface. The thickness of the pinning layer is estimated to be about9.48 nm to 15.46 nm according to the frequency shifting. These results indicate that △ fr caused by the pinning layer should be addressed in the design of microwave and spin wave devices, especially in the transverse magnetic components.展开更多
In this paper, we report a ferromagnetic resonance study on the permalloy film of submicron sized rectangular arrays prepared by electron beam lithography and the theoretical simulation to the non uniform demagnetiz...In this paper, we report a ferromagnetic resonance study on the permalloy film of submicron sized rectangular arrays prepared by electron beam lithography and the theoretical simulation to the non uniform demagnetizing effect and ferromagnetic resonance data. By theoretical simulation, the magnetization, gyromagnetic ratio and g value of the sample are determined. The theoretical curves of the dependence of the resonance field on the field orientation φ H fit well with the experimental data. When the steady magnetic field is applied near the film normal, a series of additional regular peaks (up to eight ) appeared in the FMR spectrum on the low field side of the main FMR peak. The resonance field of these side peaks decreases linearly with the peak number. The possible physical mechanism of these multiple peaks was discussed.展开更多
Ⅰ. INTRODUCTIONThe FMR spectra measurement is a useful method for investigating the physical properties of magnetic films. For instance, anisotropy fields, surface situation and bulk inhomogeneities of the film can b...Ⅰ. INTRODUCTIONThe FMR spectra measurement is a useful method for investigating the physical properties of magnetic films. For instance, anisotropy fields, surface situation and bulk inhomogeneities of the film can be inferred from the FMR spectra at various temperatures and angles θ between the normal of the film and the applied DC field.The Ca-rich charge uncompensated CaGe: YIG films have been studied for years for their interesting properties such as the anomalous minima in the magnetization versus temperature curves and so on. To gain the insight, some samples were reduced in FeCl<sub>2</sub>. A new set of FMR lines observed after reducing for 45 min is the emphasis studied in this note.展开更多
Human body temperature not only reflects vital signs,but also affects the state of various organs through blood circulation,and even affects lifespan.Here a wireless body temperature detection scheme was presented tha...Human body temperature not only reflects vital signs,but also affects the state of various organs through blood circulation,and even affects lifespan.Here a wireless body temperature detection scheme was presented that the temperature was extracted by investigating the out-of-plane(OP)ferromagnetic resonance(FMR)field of 10.2 nm thick La_(0.7)Sr_(0.3)MnO_(3)(LSMO)film using electron paramagnetic resonance(EPR)technique.Within the range of 34-42℃,the OP FMR field changes linearly with the increasing or decreasing temperature,and this variation comes from the linear responses of magnetization to the fluctuant temperature.Using this method,a tiny temperature change(<0.1℃)of organisms can be detected accurately and sensitively,which shows great potential in body temperature monitoring for humans and mammals.展开更多
Voltage control of magnetism in multiferroics,where the ferromagnetism and ferroelectricity are simultaneously exhibiting,is of great importance to achieve compact,fast and energy efficient voltage controllable magnet...Voltage control of magnetism in multiferroics,where the ferromagnetism and ferroelectricity are simultaneously exhibiting,is of great importance to achieve compact,fast and energy efficient voltage controllable magnetic/microwave devices.Particularly,these devices are widely used in radar,aircraft,cell phones and satellites,where volume,response time and energy consumption is critical.Researchers realized electric field tuning of magnetic properties like magnetization,magnetic anisotropy and permeability in varied multiferroic heterostructures such as bulk,thin films and nanostructure by different magnetoelectric(ME)coupling mechanism:strain/stress,interfacial charge,spin–electromagnetic(EM)coupling and exchange coupling,etc.In this review,we focus on voltage control of ferromagnetic resonance(FMR)in multiferroics.ME coupling-induced FMR change is critical in microwave devices,where the electric field tuning of magnetic effective anisotropic field determines the tunability of the performance of microwave devices.Experimentally,FMR measurement technique is also an important method to determine the small effective magnetic field change in small amount of magnetic material precisely due to its high sensitivity and to reveal the deep science of multiferroics,especially,voltage control of magnetism in novel mechanisms like interfacial charge,spin–EM coupling and exchange coupling.展开更多
The authors＇ theoretical investigation on the high-frequency response of magnetized metallic magnetic films showed that magnetic films may become left-handed materials （LHMs） near the ferromagnetic resonance freque...The authors＇ theoretical investigation on the high-frequency response of magnetized metallic magnetic films showed that magnetic films may become left-handed materials （LHMs） near the ferromagnetic resonance frequency of incident waves with right-handed circular polarization （RCP） and linear polarization （LP）. The frequency range where LHM exists depends on the waves polarization, the magnetic damping coefficient, and the ferromagnetic characteristic frequency corn of the film. There also exists a critical damping coefficient ac, above which the left-handed properties disappear completely.展开更多
Heusler Co2FeSi films with a uniaxial magnetic anisotropy and high ferromagnetic resonance frequency fr were deposited by an oblique sputtering technique on Ru underlayers with various thicknesses tRufrom 0 nm to 5 nm...Heusler Co2FeSi films with a uniaxial magnetic anisotropy and high ferromagnetic resonance frequency fr were deposited by an oblique sputtering technique on Ru underlayers with various thicknesses tRufrom 0 nm to 5 nm.It is revealed that the Ru underlayers reduce the grain size of Co2FeSi,dramatically enhance the magnetic anisotropy field HK induced by the internal stress from 242 Oe(1 Oe=79.5775 A·m^-1)to 582 Oe with an increment ratio of 2.4,while a low damping coefficient remains.The result of damping implies that the continuous interface between Ru and Co2FeSi induces a large in-plane anisotropic field without introducing additional external damping.As a result,excellent high-frequency soft magnetic properties with fr up to 6.69 GHz are achieved.展开更多
Ⅰ. INTRODUCTIONAs is well known, the ferromagnetic resonance linewidth reflects the microwave loss mechanism of materials. The Ca-rich CaGe: YIG films have interesting magnetic properties and optical effect on coerci...Ⅰ. INTRODUCTIONAs is well known, the ferromagnetic resonance linewidth reflects the microwave loss mechanism of materials. The Ca-rich CaGe: YIG films have interesting magnetic properties and optical effect on coercivity and conductivity, therefore it is worthwhile to study its angular dependence of linewidth. On Ca: YIG films, the angular dependence of linewidth has been studied with eddy current model. This loss mechanism in Ca: YIG films also has been evidenced by the observations of the area dependence of linewidth. On the other hand, Fe<sup>4+</sup> ions in compensation with Ca<sup>2+</sup> ions as the fast relaxers have been展开更多
The thickness-dependent magnetic anisotropy of obliquely deposited Fe(001)/Pd thin films on Mg(001) is investigated by fitting the field-dependent resonant field curve using the Kittel equation.In this study, three Fe...The thickness-dependent magnetic anisotropy of obliquely deposited Fe(001)/Pd thin films on Mg(001) is investigated by fitting the field-dependent resonant field curve using the Kittel equation.In this study, three Fe film samples with thicknesses of 50 monolayers(ML), 45 ML, and 32 ML deposited at 0°, 45°, and 55°, respectively, are used.The magnetic anisotropy constant obtained from ferromagnetic resonance(FMR) spectra exhibits a dominant fourfold magnetocrystalline anisotropy(MCA) at the normal deposition angle with larger Fe thickness.However, the in-plane uniaxial magnetic anisotropy(UMA) is induced by a higher oblique deposition angle and a smaller thickness.Its hard axis lies between the [100] and [010] directions.The FMR data-fitting analysis yields a precise measurement of smaller contributions to the magnetic anisotropy, such as in-plane UMA.Due to MCA, when the magnetic field is weaker than the saturated field,the magnetization direction does not always align with the external field.The squared frequency-dependent resonant field measurement gives an isotropic Landé g-factor of 2.07.Our results are consistent with previous experiments conducted on the magneto-optical Kerr effect(MOKE) and anisotropic magnetoresistance(AMR) systems.Thus, a vector network analyzer ferromagnetic resonance(VNA-FMR) test-method for finding UMA in obliquely deposited Fe(001)/Pd bilayer ferromagnetic thin films, and determining the magnetic anisotropy constants with respect to the film normal deposition, is proposed.展开更多
In this paper a systematic ferromagnetic resonance study shows that an in-plane magnetic anisotropy in the patterned micron octagon permalloy （Ni80Fe20） elements is mainly determined by the element geometry. The eas...In this paper a systematic ferromagnetic resonance study shows that an in-plane magnetic anisotropy in the patterned micron octagon permalloy （Ni80Fe20） elements is mainly determined by the element geometry. The easy-axis is along the edge of the elements, and the hard-axis is along the diagonal. The shape anisotropy of the octagon elements is determined by square and equilateral octagon, and the theoretical calculation was studied on the shape anisotropy. The shape anisotropy of rectangular was calculated by using the same theory.展开更多
CoNiFe patterned films with rectangular elements, all 600-nm wide but of different lengths, were fabricated and inves- tigated by ferromagnetic resonance experiment and micromagnetic simulation. An in-plane magnetic u...CoNiFe patterned films with rectangular elements, all 600-nm wide but of different lengths, were fabricated and inves- tigated by ferromagnetic resonance experiment and micromagnetic simulation. An in-plane magnetic uniaxial anisotropy was exhibited, and its value increases with the increase of the aspect ratio of the elements, which was fitted by the model, including a quasi-ellipsoid demagnetizing field and a non-uniform demagnetizing field. The relative importance of the non- uniform demagnetizing field decreased from 0.26 to 0.16 with the increase of the length-width aspect ratio of the patterned element from 1.5 to 10. The demagnetizing factors in the three principal axes were determined from the experimental data of ferromagnetic resonance, which agreed reasonably well with the values calculated by micromagnetic simulation. The calculation also indicated that the interaction between elements could be neglected when the edge-to-edge spacing between neighboring elements was larger than 3 μm in our patterned films.展开更多
基金National Natural Science Foundation of China(Grant Nos.11674187 and 51871127)Technology on Electronic Test&Measurement Laboratory(Grant No.6142001180103).
文摘Nowadays the yttrium iron garnet(Y3Fe5O12, YIG) films are widely used in the microwave and spin wave devices due to their low damping constant and long propagation distance for spin waves. However, the performances, especially the frequency stability, are seriously affected by the relaxation of the interface magnetic moments. In this study, the effect of out-of-plane magnetization depinning on the resonance frequency shift(△ fr) was investigated for 3-μm YIG films grown on Gd3Ga5O12(GGG)(111) substrates by liquid-phase epitaxy. It is revealed that the ferromagnetic resonance(FMR) and spin wave propagation exhibit a very slow relaxation with relaxation time τ even longer than one hour under an out-of-plane external magnetic bias field. The △ fr span of 15.15–24.70 MHz is observed in out-of-plane FMR and forward volume spin waves. Moreover, the △ fr and τ depend on the magnetic field. The △ fr can be attributed to that the magnetic moments break away from the pinning layer at the YIG/GGG interface. The thickness of the pinning layer is estimated to be about9.48 nm to 15.46 nm according to the frequency shifting. These results indicate that △ fr caused by the pinning layer should be addressed in the design of microwave and spin wave devices, especially in the transverse magnetic components.
文摘In this paper, we report a ferromagnetic resonance study on the permalloy film of submicron sized rectangular arrays prepared by electron beam lithography and the theoretical simulation to the non uniform demagnetizing effect and ferromagnetic resonance data. By theoretical simulation, the magnetization, gyromagnetic ratio and g value of the sample are determined. The theoretical curves of the dependence of the resonance field on the field orientation φ H fit well with the experimental data. When the steady magnetic field is applied near the film normal, a series of additional regular peaks (up to eight ) appeared in the FMR spectrum on the low field side of the main FMR peak. The resonance field of these side peaks decreases linearly with the peak number. The possible physical mechanism of these multiple peaks was discussed.
文摘Ⅰ. INTRODUCTIONThe FMR spectra measurement is a useful method for investigating the physical properties of magnetic films. For instance, anisotropy fields, surface situation and bulk inhomogeneities of the film can be inferred from the FMR spectra at various temperatures and angles θ between the normal of the film and the applied DC field.The Ca-rich charge uncompensated CaGe: YIG films have been studied for years for their interesting properties such as the anomalous minima in the magnetization versus temperature curves and so on. To gain the insight, some samples were reduced in FeCl<sub>2</sub>. A new set of FMR lines observed after reducing for 45 min is the emphasis studied in this note.
基金This work was supported by the Doctoral Startup Foundation of Taiyuan University of Science and Technology(Grant No.20202042)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(Grant No.2021L303)+4 种基金the Excellent Doctoral Foundation of Shanxi Province(Grant No.20212044)the National Key R&D Program of China(Grant No.2018YFB0407601)the National Natural Science Foundation of China(Grant Nos.11534015,51602244 and 11804266)the National 111 Project of China(Grant No.B14040)the Fundamental Research Funds for the Central Universities(Grant No.xzy022019069).
文摘Human body temperature not only reflects vital signs,but also affects the state of various organs through blood circulation,and even affects lifespan.Here a wireless body temperature detection scheme was presented that the temperature was extracted by investigating the out-of-plane(OP)ferromagnetic resonance(FMR)field of 10.2 nm thick La_(0.7)Sr_(0.3)MnO_(3)(LSMO)film using electron paramagnetic resonance(EPR)technique.Within the range of 34-42℃,the OP FMR field changes linearly with the increasing or decreasing temperature,and this variation comes from the linear responses of magnetization to the fluctuant temperature.Using this method,a tiny temperature change(<0.1℃)of organisms can be detected accurately and sensitively,which shows great potential in body temperature monitoring for humans and mammals.
基金the Natural Science Foundation of China(Grant Nos.51472199,11534015)the National 111 Project of China(B14040)the Beijing Institute of Technology Research Fund Program for Young Scholars(Grant No.3050012261527)。
文摘Voltage control of magnetism in multiferroics,where the ferromagnetism and ferroelectricity are simultaneously exhibiting,is of great importance to achieve compact,fast and energy efficient voltage controllable magnetic/microwave devices.Particularly,these devices are widely used in radar,aircraft,cell phones and satellites,where volume,response time and energy consumption is critical.Researchers realized electric field tuning of magnetic properties like magnetization,magnetic anisotropy and permeability in varied multiferroic heterostructures such as bulk,thin films and nanostructure by different magnetoelectric(ME)coupling mechanism:strain/stress,interfacial charge,spin–electromagnetic(EM)coupling and exchange coupling,etc.In this review,we focus on voltage control of ferromagnetic resonance(FMR)in multiferroics.ME coupling-induced FMR change is critical in microwave devices,where the electric field tuning of magnetic effective anisotropic field determines the tunability of the performance of microwave devices.Experimentally,FMR measurement technique is also an important method to determine the small effective magnetic field change in small amount of magnetic material precisely due to its high sensitivity and to reveal the deep science of multiferroics,especially,voltage control of magnetism in novel mechanisms like interfacial charge,spin–EM coupling and exchange coupling.
基金Project supported by the National Basic Research Program (973) ofChina (No. 2004CB719805) and the National Natural Science Foun-dation of China (No. 60471020)
文摘The authors＇ theoretical investigation on the high-frequency response of magnetized metallic magnetic films showed that magnetic films may become left-handed materials （LHMs） near the ferromagnetic resonance frequency of incident waves with right-handed circular polarization （RCP） and linear polarization （LP）. The frequency range where LHM exists depends on the waves polarization, the magnetic damping coefficient, and the ferromagnetic characteristic frequency corn of the film. There also exists a critical damping coefficient ac, above which the left-handed properties disappear completely.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674187 and 51871127)the Fund from the Technology on Electronic Test&Measurement Laboratory(Grant No.6142001180103)。
文摘Heusler Co2FeSi films with a uniaxial magnetic anisotropy and high ferromagnetic resonance frequency fr were deposited by an oblique sputtering technique on Ru underlayers with various thicknesses tRufrom 0 nm to 5 nm.It is revealed that the Ru underlayers reduce the grain size of Co2FeSi,dramatically enhance the magnetic anisotropy field HK induced by the internal stress from 242 Oe(1 Oe=79.5775 A·m^-1)to 582 Oe with an increment ratio of 2.4,while a low damping coefficient remains.The result of damping implies that the continuous interface between Ru and Co2FeSi induces a large in-plane anisotropic field without introducing additional external damping.As a result,excellent high-frequency soft magnetic properties with fr up to 6.69 GHz are achieved.
文摘Ⅰ. INTRODUCTIONAs is well known, the ferromagnetic resonance linewidth reflects the microwave loss mechanism of materials. The Ca-rich CaGe: YIG films have interesting magnetic properties and optical effect on coercivity and conductivity, therefore it is worthwhile to study its angular dependence of linewidth. On Ca: YIG films, the angular dependence of linewidth has been studied with eddy current model. This loss mechanism in Ca: YIG films also has been evidenced by the observations of the area dependence of linewidth. On the other hand, Fe<sup>4+</sup> ions in compensation with Ca<sup>2+</sup> ions as the fast relaxers have been
基金Project supported by the National Basic Research Program of China(Grant Nos.2015CB921403 and 2016YFA0300701)the National Natural Science Foundation of China(Grant Nos.51427801,11374350,and 51671212)the Chinese Government Scholarship(Grant No.2015GXYG37)
文摘The thickness-dependent magnetic anisotropy of obliquely deposited Fe(001)/Pd thin films on Mg(001) is investigated by fitting the field-dependent resonant field curve using the Kittel equation.In this study, three Fe film samples with thicknesses of 50 monolayers(ML), 45 ML, and 32 ML deposited at 0°, 45°, and 55°, respectively, are used.The magnetic anisotropy constant obtained from ferromagnetic resonance(FMR) spectra exhibits a dominant fourfold magnetocrystalline anisotropy(MCA) at the normal deposition angle with larger Fe thickness.However, the in-plane uniaxial magnetic anisotropy(UMA) is induced by a higher oblique deposition angle and a smaller thickness.Its hard axis lies between the [100] and [010] directions.The FMR data-fitting analysis yields a precise measurement of smaller contributions to the magnetic anisotropy, such as in-plane UMA.Due to MCA, when the magnetic field is weaker than the saturated field,the magnetization direction does not always align with the external field.The squared frequency-dependent resonant field measurement gives an isotropic Landé g-factor of 2.07.Our results are consistent with previous experiments conducted on the magneto-optical Kerr effect(MOKE) and anisotropic magnetoresistance(AMR) systems.Thus, a vector network analyzer ferromagnetic resonance(VNA-FMR) test-method for finding UMA in obliquely deposited Fe(001)/Pd bilayer ferromagnetic thin films, and determining the magnetic anisotropy constants with respect to the film normal deposition, is proposed.
基金Project supported by the National Natural Science Foundation of China （Grant No 50171020） and the Foundation for youth of Liaocheng University （Grant No X051050）.
文摘In this paper a systematic ferromagnetic resonance study shows that an in-plane magnetic anisotropy in the patterned micron octagon permalloy （Ni80Fe20） elements is mainly determined by the element geometry. The easy-axis is along the edge of the elements, and the hard-axis is along the diagonal. The shape anisotropy of the octagon elements is determined by square and equilateral octagon, and the theoretical calculation was studied on the shape anisotropy. The shape anisotropy of rectangular was calculated by using the same theory.
基金Project supported by the Postgraduates Innovation Program of Jiangsu Province, China (Grant No. CXZZ12-0086)the National Natural Science Foundation of China (Grant No. 11074034)+1 种基金the National Basic Research Program of China (Grant No. 2010CB923404)the National Laboratory of Solid State Microstructures at Nanjing University and Southeast University, China
文摘CoNiFe patterned films with rectangular elements, all 600-nm wide but of different lengths, were fabricated and inves- tigated by ferromagnetic resonance experiment and micromagnetic simulation. An in-plane magnetic uniaxial anisotropy was exhibited, and its value increases with the increase of the aspect ratio of the elements, which was fitted by the model, including a quasi-ellipsoid demagnetizing field and a non-uniform demagnetizing field. The relative importance of the non- uniform demagnetizing field decreased from 0.26 to 0.16 with the increase of the length-width aspect ratio of the patterned element from 1.5 to 10. The demagnetizing factors in the three principal axes were determined from the experimental data of ferromagnetic resonance, which agreed reasonably well with the values calculated by micromagnetic simulation. The calculation also indicated that the interaction between elements could be neglected when the edge-to-edge spacing between neighboring elements was larger than 3 μm in our patterned films.
