We study the interfacial Dzyaloshinskii-Moriya interactions(i-DMI)of Fe/Pt bilayers grown on Si substrates with MgO,SiO_(2),or Ta each as a buffer layer on the basis of wave-vector-resolved Brillouin light scattering(...We study the interfacial Dzyaloshinskii-Moriya interactions(i-DMI)of Fe/Pt bilayers grown on Si substrates with MgO,SiO_(2),or Ta each as a buffer layer on the basis of wave-vector-resolved Brillouin light scattering(BLS)measurement.The obtained i-DMI energy values for Fe/Pt on MgO,Ta,and SiO_(2) buffer layers are 0.359,0.321,and 0.274 mJ/m~2,respectively.The large i-DMI value observed in Fe/Pt system on the MgO buffer layer can be attributed to the good interfacial quality and the Rshaba effect at the MgO/Fe interface.Moreover,the MgO/Fe/Pt system,benefiting from better sample quality,exhibits a lower damping factor.Furthermore,layer-resolved first-principles calculations are carried out to gain a more in-depth understanding of the origin of the i-DMI in the Fe/Pt system.The results indicate that in the Fe(110)/Pt(111)system,the substantial DMI energy between Fe spins at the interface is related to a significant change in spin-orbit coupling(SOC)energy in the neighboring Pt layer.In contrast,for the MgO(002)/Fe(002)system,both the DMI and its related SOC energy are concentrated at the interfacial Fe layer.Our investigation will provide a valuable insight into the spintronic community in exploring novel devices with chirality dependence.展开更多
Interfacial magnetic anisotropy in a Pt/CO1-xFex/Pt multilayer is tuned by doping iron atoms into the cobalt layer. The perpendicular magnetic anisotropy and out-of-plane coercivity are found to decrease with increasi...Interfacial magnetic anisotropy in a Pt/CO1-xFex/Pt multilayer is tuned by doping iron atoms into the cobalt layer. The perpendicular magnetic anisotropy and out-of-plane coercivity are found to decrease with increasing x. For a specific x, the out-of-plane coercivity acquires a maximal value as a function of the thickness of the CoFe layer. At low temperature, the coercivity is enhanced. Small coercivity but reasonably large perpendicular magnetic anisotropy can be obtained by controlling the x and CoFe layer thickness.展开更多
Thanks to the strong perpendicular magnetic anisotropy(PMA), excellent processing compatibility as well as novel spintronic phenomenon, Co/Pt multilayers have been attracting massive attention and widely used in magne...Thanks to the strong perpendicular magnetic anisotropy(PMA), excellent processing compatibility as well as novel spintronic phenomenon, Co/Pt multilayers have been attracting massive attention and widely used in magnetic storage.However, reversed magnetic domains come into being with the increasing layer repetition ‘N’ to reduce magneto-static energy, resulting in the remarkable diminishment of the remanent magnetization(Mr). As a result, the product of Mrand thickness(i.e., the remanent moment-thickness product, Mrt), a key parameter in magnetic recording for reliable data storing and reading, also decreases dramatically. To overcome this issue, we deposit an ultra-thick granular [Co/Pt]80multilayer with a total thickness of 68 nm on granular SiNxbuffer layer. The Mrt value, Mrto saturation magnetization(Ms) ratio as well as out of plane(OOP) coercivity(Hcoop) are high up to 2.97 memu/cm^(2), 67%, and 1940 Oe(1 Oe = 79.5775 A·m^(-1)),respectively, which is remarkably improved compared with that of continuous [Co/Pt]80multilayers. That is because large amounts of grain boundaries in the granular multilayers can efficiently impede the propagation and expansion of reversed magnetic domains, which is verified by experimental investigations and micromagnetic simulation results. The simulation results also indicate that the value of Mrt, Mr/Msratio, and Hcoopcan be further improved through optimizing the granule size, which can be experimentally realized by manipulating the process parameter of SiNxbuffer layer. This work provides an alternative solution for achieving high Mrt value in ultra-thick Co/Pt multilayers, which is of unneglectable potential in applications of high-density magnetic recording.展开更多
Out-of-plane angular dependence of ferromagnetic resonance spectra was measured in sputtered Co/Pt multilayers and analyzed with the Landau-Lifshitz-Gilbert equation. The effective demagnetizing field 4πMeff is found...Out-of-plane angular dependence of ferromagnetic resonance spectra was measured in sputtered Co/Pt multilayers and analyzed with the Landau-Lifshitz-Gilbert equation. The effective demagnetizing field 4πMeff is found to increase with decreasing tPt and decreasing 1/tco, which can be considered as a result of interplay between the interlayer coupling and a lowdimensional effect. The g factor increases with increasing tpt and decreasing tCo, indicating contribution of spin-polarization of Pt atoms and additional contribution of orbital moment of Co atoms. The in-plane resonance line-width increases with decreasing too and increases with increasing tPt.展开更多
Ag/Fe multilayers with well compositional modulation periodicity of 4-60 nm were prepared at room temperature by evaporation deposition using an ultra high vacuum (UHV) chamber. Their microstructure and hardness were ...Ag/Fe multilayers with well compositional modulation periodicity of 4-60 nm were prepared at room temperature by evaporation deposition using an ultra high vacuum (UHV) chamber. Their microstructure and hardness were investigated using XRD, TEM and nanoindentation. The fcc/bcc type multilayers show a textured polycrystalline growth with Ag (111) and Fe (110) in Ag layers and Fe layers, respectively. The hardness increases with decreasing periodicity and approaches the maximum of 6.36 GPa at the periodicity of 4 nm. The peak hardness is 1.51 times mixture value. The experimental results are well explained by the dislocation-image force-based model developed by Lehoczky.展开更多
Magnetic properties and microstructure of Fe/RE multilayers(thickness of Fe single layers less than or equal to 2.0 nm) both as-deposited state and after annealing( T greater than or equal to 473 K) were studied, and ...Magnetic properties and microstructure of Fe/RE multilayers(thickness of Fe single layers less than or equal to 2.0 nm) both as-deposited state and after annealing( T greater than or equal to 473 K) were studied, and the reason of the change of magnetic properties was analyzed. The Fe single layers are considered to be composed of insular Fe domains in as-deposited films. Super-paramagnetic nature of the Fe domains of small size causes the films to exhibit paramagnetism. During annealing the growth of Fe domains results in the transformation of films from paramagnetic into ferromagnetic, which leads to the increase in H-c and M-s.展开更多
Hysteresis loops,energy products and magnetic moment distributions of perpendicularly oriented Nd2Fe(14)B/α-Fe exchange-spring multilayers are studied systematically based on both three-dimensional(3D)and one-dimensi...Hysteresis loops,energy products and magnetic moment distributions of perpendicularly oriented Nd2Fe(14)B/α-Fe exchange-spring multilayers are studied systematically based on both three-dimensional(3D)and one-dimensional(1D)micromagnetic methods,focused on the influence of the interface anisotropy.The calculated results are carefully compared with each other.The interface anisotropy effect is very palpable on the nucleation,pinning and coercive fields when the soft layer is very thin.However,as the soft layer thickness increases,the pinning and coercive fields are almost unchanged with the increment of interface anisotropy though the nucleation field still monotonically rises.Negative interface anisotropy decreases the maximum energy products and increases slightly the angles between the magnetization and applied field.The magnetic moment distributions in the thickness direction at various applied fields demonstrate a progress of three-step magnetic reversal,i.e.,nucleation,evolution and irreversible motion of the domain wall.The above results calculated by two models are in good agreement with each other.Moreover,the in-plane magnetic moment orientations based on two models are different.The 3D calculation shows a progress of generation and disappearance of vortex state,however,the magnetization orientations within the film plane calculated by the 1D model are coherent.Simulation results suggest that negative interface anisotropy is necessarily avoided experimentally.展开更多
RE/Fe multilayer films were prepared by alternate deposition of the two elements onto Si or NaCl single crystal substrates(RE=Dy, Y). The changes in structure of the films were analyzed in situ on the transmission ele...RE/Fe multilayer films were prepared by alternate deposition of the two elements onto Si or NaCl single crystal substrates(RE=Dy, Y). The changes in structure of the films were analyzed in situ on the transmission electron microscope(TEM) hot stage, and were studied by Xray diffraction(XRD) after annealing under vacuum. It was found that, annealing at temperature≤200 ℃ for a long time(～300 min), the amorphous state and the modulated structure of asdeposited films remained basically unchanged. It is suggested that RE/Fe multilayers are stable at temperature up to 200 ℃.〖HS*2]展开更多
Ni0.7Zn0.3Fe2O4/Co0.8Fe2.2O4（NZFO/CFO） multilayer films are fabricated on Si（lO0） substrates by the chemical solution deposition method. The mierostructure and magnetic properties are systematically investigated. ...Ni0.7Zn0.3Fe2O4/Co0.8Fe2.2O4（NZFO/CFO） multilayer films are fabricated on Si（lO0） substrates by the chemical solution deposition method. The mierostructure and magnetic properties are systematically investigated. The results of field-emission scanning electronic microscopy show that the grain size of the NZFO/CFO multilayer film is quite uniform and the thickness is about 30Ohm. The remanence enhancement effect of the NZFO/CFO multilayer film can be mainly attributed to the exchange coupling interaction between NZFO and CFO ferrite films, which is in favor of the design and fabrication of modern electronic devices.展开更多
Fe/Ti multilayers with different modulation wavelengths (Lambda) prepared by r.f. sputtering has been investigated by using cross sectional transmission electron microscopy (XTEM). It was observed that the columnar st...Fe/Ti multilayers with different modulation wavelengths (Lambda) prepared by r.f. sputtering has been investigated by using cross sectional transmission electron microscopy (XTEM). It was observed that the columnar structure, interface morphology, and metastable phase presented at the interface of the multilayer system strongly depend on the bilayer thickness (Lambda). For high period multilayers, the waviness wavelength of interfaces is about two times broader than the column diameter. For a sample with Lambda =30 nm, its column width and waviness wavelength was about 80, and 190 nm, respectively. Both of them decreased with the reduction of Lambda, so as to nearly equal values of column diameter and waviness wavelength were obtained. The Fe and Ti grains of both 30 nm and 6 nm multilayers are polycrystalline, and have a textured structure. In short bilayer thickness (Lambda =6 nm), the intermetallic compound Fe2Ti was presented at the interfaces due to solid state reaction; for Lambda =2 nm, amorphous phase Ti-rich layer was formed at the interfaces, resulting in a sharp interface multilayer structure.展开更多
Co/Pt multilayers with perpendicular anisotropy were deposited using a dc magnetron sputtering system under high vacuum.Magnetization process was investigated by the measurement of magnetic components parallel and per...Co/Pt multilayers with perpendicular anisotropy were deposited using a dc magnetron sputtering system under high vacuum.Magnetization process was investigated by the measurement of magnetic components parallel and perpendicular to the applied field.A dependence of the coercivity of Co/Pt multilayers on the Co layer thickness was reported,in which the total thickness of Co layers kept constant.It is observed that the coercivity increases with the increment of Co layer thickness.For the samples with the same Co layer thickness while different total Co layer thickness,the coercivity first increases and then decreases with the increase of the total thickness of Co layers.This effect could be attributed to the competition between the reduction of HC related to incoherent reversal and the step-up of HC contributed by the magnetic polarization of Pt atoms at the interface of Co and Pt layers during magnetization reversal.The results show that the change of the coercivity is strongly related to the Co layer thickness,but not the total thickness of Co layers.The dependence of the coercivity on the angle between an applied field and the easy axis shows that the nucleation mode is dominant in magnetization reversal process of the samples.展开更多
Fe/C multilayer thin films were deposited by magnetron sputtering. Small angle X-ray diffraction measurements show very well periodicity of the samples. The modulation period determined from a modified Bragg equation ...Fe/C multilayer thin films were deposited by magnetron sputtering. Small angle X-ray diffraction measurements show very well periodicity of the samples. The modulation period determined from a modified Bragg equation agrees well with that determined from deposition rate. The interfacial roughness parameter ξof several samples calculated by X-ray diffraction is between 3.5(?) and 5.6(?).展开更多
基金Project supported by the National Basic Research Program of China (Grant Nos.12074220,12304151,12204355,and 12204356)the Natural Science Foundation of Shandong Province,China (Grant No.ZR2022QA085)。
文摘We study the interfacial Dzyaloshinskii-Moriya interactions(i-DMI)of Fe/Pt bilayers grown on Si substrates with MgO,SiO_(2),or Ta each as a buffer layer on the basis of wave-vector-resolved Brillouin light scattering(BLS)measurement.The obtained i-DMI energy values for Fe/Pt on MgO,Ta,and SiO_(2) buffer layers are 0.359,0.321,and 0.274 mJ/m~2,respectively.The large i-DMI value observed in Fe/Pt system on the MgO buffer layer can be attributed to the good interfacial quality and the Rshaba effect at the MgO/Fe interface.Moreover,the MgO/Fe/Pt system,benefiting from better sample quality,exhibits a lower damping factor.Furthermore,layer-resolved first-principles calculations are carried out to gain a more in-depth understanding of the origin of the i-DMI in the Fe/Pt system.The results indicate that in the Fe(110)/Pt(111)system,the substantial DMI energy between Fe spins at the interface is related to a significant change in spin-orbit coupling(SOC)energy in the neighboring Pt layer.In contrast,for the MgO(002)/Fe(002)system,both the DMI and its related SOC energy are concentrated at the interfacial Fe layer.Our investigation will provide a valuable insight into the spintronic community in exploring novel devices with chirality dependence.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11074112,10974032,and 51201114)the National Basic Research Program of China (Grant Nos. 2009CB929201 and 2010CB923401)the Key Project of the Chinese Ministry of Education (Grant No. 210074)
文摘Interfacial magnetic anisotropy in a Pt/CO1-xFex/Pt multilayer is tuned by doping iron atoms into the cobalt layer. The perpendicular magnetic anisotropy and out-of-plane coercivity are found to decrease with increasing x. For a specific x, the out-of-plane coercivity acquires a maximal value as a function of the thickness of the CoFe layer. At low temperature, the coercivity is enhanced. Small coercivity but reasonably large perpendicular magnetic anisotropy can be obtained by controlling the x and CoFe layer thickness.
基金supported by the National Natural Science Foundation of China (Grant No. 51901008)the National Key Research and Development Program of China (Grant No. 2021YFB3201800)。
文摘Thanks to the strong perpendicular magnetic anisotropy(PMA), excellent processing compatibility as well as novel spintronic phenomenon, Co/Pt multilayers have been attracting massive attention and widely used in magnetic storage.However, reversed magnetic domains come into being with the increasing layer repetition ‘N’ to reduce magneto-static energy, resulting in the remarkable diminishment of the remanent magnetization(Mr). As a result, the product of Mrand thickness(i.e., the remanent moment-thickness product, Mrt), a key parameter in magnetic recording for reliable data storing and reading, also decreases dramatically. To overcome this issue, we deposit an ultra-thick granular [Co/Pt]80multilayer with a total thickness of 68 nm on granular SiNxbuffer layer. The Mrt value, Mrto saturation magnetization(Ms) ratio as well as out of plane(OOP) coercivity(Hcoop) are high up to 2.97 memu/cm^(2), 67%, and 1940 Oe(1 Oe = 79.5775 A·m^(-1)),respectively, which is remarkably improved compared with that of continuous [Co/Pt]80multilayers. That is because large amounts of grain boundaries in the granular multilayers can efficiently impede the propagation and expansion of reversed magnetic domains, which is verified by experimental investigations and micromagnetic simulation results. The simulation results also indicate that the value of Mrt, Mr/Msratio, and Hcoopcan be further improved through optimizing the granule size, which can be experimentally realized by manipulating the process parameter of SiNxbuffer layer. This work provides an alternative solution for achieving high Mrt value in ultra-thick Co/Pt multilayers, which is of unneglectable potential in applications of high-density magnetic recording.
基金Project supported by the National Natural Science Foundation of China （Grant Nos.10504019, 10574087）, and the Shanghai Leading Academic Disciplines Program （Grant No.T0104）
文摘Out-of-plane angular dependence of ferromagnetic resonance spectra was measured in sputtered Co/Pt multilayers and analyzed with the Landau-Lifshitz-Gilbert equation. The effective demagnetizing field 4πMeff is found to increase with decreasing tPt and decreasing 1/tco, which can be considered as a result of interplay between the interlayer coupling and a lowdimensional effect. The g factor increases with increasing tpt and decreasing tCo, indicating contribution of spin-polarization of Pt atoms and additional contribution of orbital moment of Co atoms. The in-plane resonance line-width increases with decreasing too and increases with increasing tPt.
基金Projects(50871060, 50772055) supported by the National Natural Science Foundation of ChinaProject(2007AA03Z426) supported by High-tech Research and Development Program of China
文摘Ag/Fe multilayers with well compositional modulation periodicity of 4-60 nm were prepared at room temperature by evaporation deposition using an ultra high vacuum (UHV) chamber. Their microstructure and hardness were investigated using XRD, TEM and nanoindentation. The fcc/bcc type multilayers show a textured polycrystalline growth with Ag (111) and Fe (110) in Ag layers and Fe layers, respectively. The hardness increases with decreasing periodicity and approaches the maximum of 6.36 GPa at the periodicity of 4 nm. The peak hardness is 1.51 times mixture value. The experimental results are well explained by the dislocation-image force-based model developed by Lehoczky.
文摘Magnetic properties and microstructure of Fe/RE multilayers(thickness of Fe single layers less than or equal to 2.0 nm) both as-deposited state and after annealing( T greater than or equal to 473 K) were studied, and the reason of the change of magnetic properties was analyzed. The Fe single layers are considered to be composed of insular Fe domains in as-deposited films. Super-paramagnetic nature of the Fe domains of small size causes the films to exhibit paramagnetism. During annealing the growth of Fe domains results in the transformation of films from paramagnetic into ferromagnetic, which leads to the increase in H-c and M-s.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB0700900)the National Natural Science Foundation of China(Grant Nos.51571126 and 51861030)+1 种基金the Inner Mongolia Autonomous Region Natural Science Foundation of China(Grant No.2019MS01002)the Inner Mongolia Innovative Research Team of China(Grant No.3400102)。
文摘Hysteresis loops,energy products and magnetic moment distributions of perpendicularly oriented Nd2Fe(14)B/α-Fe exchange-spring multilayers are studied systematically based on both three-dimensional(3D)and one-dimensional(1D)micromagnetic methods,focused on the influence of the interface anisotropy.The calculated results are carefully compared with each other.The interface anisotropy effect is very palpable on the nucleation,pinning and coercive fields when the soft layer is very thin.However,as the soft layer thickness increases,the pinning and coercive fields are almost unchanged with the increment of interface anisotropy though the nucleation field still monotonically rises.Negative interface anisotropy decreases the maximum energy products and increases slightly the angles between the magnetization and applied field.The magnetic moment distributions in the thickness direction at various applied fields demonstrate a progress of three-step magnetic reversal,i.e.,nucleation,evolution and irreversible motion of the domain wall.The above results calculated by two models are in good agreement with each other.Moreover,the in-plane magnetic moment orientations based on two models are different.The 3D calculation shows a progress of generation and disappearance of vortex state,however,the magnetization orientations within the film plane calculated by the 1D model are coherent.Simulation results suggest that negative interface anisotropy is necessarily avoided experimentally.
文摘RE/Fe multilayer films were prepared by alternate deposition of the two elements onto Si or NaCl single crystal substrates(RE=Dy, Y). The changes in structure of the films were analyzed in situ on the transmission electron microscope(TEM) hot stage, and were studied by Xray diffraction(XRD) after annealing under vacuum. It was found that, annealing at temperature≤200 ℃ for a long time(～300 min), the amorphous state and the modulated structure of asdeposited films remained basically unchanged. It is suggested that RE/Fe multilayers are stable at temperature up to 200 ℃.〖HS*2]
基金Supported by the National Natural Science Foundation of China under Grant Nos 11274314,11374304,51102072,21201052 and U1632161the Natural Science Major Foundation of Anhui Provincial Higher Education Institutions under Grant No KJ2012ZD14+2 种基金the Natural Science Foundation of Anhui Province under Grant No 1508085MA18the Postdoctoral Science Foundation of China under Grant No 2013M541848the Foundation for University Key Teachers from Hefei Normal University under Grant No2014136JKC08
文摘Ni0.7Zn0.3Fe2O4/Co0.8Fe2.2O4（NZFO/CFO） multilayer films are fabricated on Si（lO0） substrates by the chemical solution deposition method. The mierostructure and magnetic properties are systematically investigated. The results of field-emission scanning electronic microscopy show that the grain size of the NZFO/CFO multilayer film is quite uniform and the thickness is about 30Ohm. The remanence enhancement effect of the NZFO/CFO multilayer film can be mainly attributed to the exchange coupling interaction between NZFO and CFO ferrite films, which is in favor of the design and fabrication of modern electronic devices.
基金Financial support from National Natural Science Foundation of China and the Ministry of Science&Technology of China(Grant No.(1999064505)is acknowledged.
文摘Fe/Ti multilayers with different modulation wavelengths (Lambda) prepared by r.f. sputtering has been investigated by using cross sectional transmission electron microscopy (XTEM). It was observed that the columnar structure, interface morphology, and metastable phase presented at the interface of the multilayer system strongly depend on the bilayer thickness (Lambda). For high period multilayers, the waviness wavelength of interfaces is about two times broader than the column diameter. For a sample with Lambda =30 nm, its column width and waviness wavelength was about 80, and 190 nm, respectively. Both of them decreased with the reduction of Lambda, so as to nearly equal values of column diameter and waviness wavelength were obtained. The Fe and Ti grains of both 30 nm and 6 nm multilayers are polycrystalline, and have a textured structure. In short bilayer thickness (Lambda =6 nm), the intermetallic compound Fe2Ti was presented at the interfaces due to solid state reaction; for Lambda =2 nm, amorphous phase Ti-rich layer was formed at the interfaces, resulting in a sharp interface multilayer structure.
基金Projects(10574065,20833002) supported by the National Natural Science Foundation of ChinaProject(2009CB929503) supported by the National Basic Research Program of China
文摘Co/Pt multilayers with perpendicular anisotropy were deposited using a dc magnetron sputtering system under high vacuum.Magnetization process was investigated by the measurement of magnetic components parallel and perpendicular to the applied field.A dependence of the coercivity of Co/Pt multilayers on the Co layer thickness was reported,in which the total thickness of Co layers kept constant.It is observed that the coercivity increases with the increment of Co layer thickness.For the samples with the same Co layer thickness while different total Co layer thickness,the coercivity first increases and then decreases with the increase of the total thickness of Co layers.This effect could be attributed to the competition between the reduction of HC related to incoherent reversal and the step-up of HC contributed by the magnetic polarization of Pt atoms at the interface of Co and Pt layers during magnetization reversal.The results show that the change of the coercivity is strongly related to the Co layer thickness,but not the total thickness of Co layers.The dependence of the coercivity on the angle between an applied field and the easy axis shows that the nucleation mode is dominant in magnetization reversal process of the samples.
文摘Fe/C multilayer thin films were deposited by magnetron sputtering. Small angle X-ray diffraction measurements show very well periodicity of the samples. The modulation period determined from a modified Bragg equation agrees well with that determined from deposition rate. The interfacial roughness parameter ξof several samples calculated by X-ray diffraction is between 3.5(?) and 5.6(?).
