The effect of ultrathin Fe layer on perpendicular magnetic anisotropy(PMA) in magnetron-sputtered Co/Pt multilayers was investigated by magnetic measurements.Magnetization hysteresis(M-H) loops and microstructures of ...The effect of ultrathin Fe layer on perpendicular magnetic anisotropy(PMA) in magnetron-sputtered Co/Pt multilayers was investigated by magnetic measurements.Magnetization hysteresis(M-H) loops and microstructures of the samples were measured by vibrating sample magnetometer(VSM) and X-ray diffraction(XRD) and highresolution transmission electron microscopy(HRTEM),respectively.It is found that the PMA is strongly dependent on the interface where Fe layer was doped.When Fe layer was doped at Co/Pt interface where Pt was deposited on Co,the PMA decreases monotonically with Fe layer thickness(tFe) increasing.However,when Fe layer was doped at Pt/Co interface where Co was deposited on Pt,the PMA shows a peak at t_(Fe)=0.1 nm.It is considered that the PMA variation is mainly due to the tuning in the electron occupation states of 3 d orbits at Fe-doped Pt/Co interface.Furthermore,the annealing stability of PMA can also be improved when Fe layer was doped at Pt/Co interface.HRTEM results demonstrate that the magnetic anisotropy evolution is mainly caused by anneal-induced interdiffusion.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
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
The dependence of perpendicular magnetic anisotropy （PMA） on the barrier layer MgO thickness in MgO/CoFeB /Ta multilayers is investigated. The results show that the strongest PMA occurs in a small window of about 2 ...The dependence of perpendicular magnetic anisotropy （PMA） on the barrier layer MgO thickness in MgO/CoFeB /Ta multilayers is investigated. The results show that the strongest PMA occurs in a small window of about 2 4nm with the increase of MgO thickness from 1-1Onto. The crystalline degree of MgO and the change of interatomic distance along the out-of-plane direction may be the main reasons for the change of PMA in these multilayers. Moreover, the roughnesses of 2- and 4-nm-thick MgO samples are 3.163 and 1.8 nm, respectively, and both the samples show PMA. These results could be used to tune the magnetic characteristic of the ultra thin CoFeB film for future applications in perpendicular magnetic devices.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
采用磁控溅射方法在玻璃基片上制备了以Ru,Cu,Pt和Ta为底层的Co Fe B/Pt多层膜样品,研究了各底层对Co Fe B/Pt多层膜的反常霍尔效应的影响。发现Ru和Cu作为Co Fe B/Pt多层膜的底层在保持样品的垂直磁各向异性方面的作用远不如Pt和Ta底层...采用磁控溅射方法在玻璃基片上制备了以Ru,Cu,Pt和Ta为底层的Co Fe B/Pt多层膜样品,研究了各底层对Co Fe B/Pt多层膜的反常霍尔效应的影响。发现Ru和Cu作为Co Fe B/Pt多层膜的底层在保持样品的垂直磁各向异性方面的作用远不如Pt和Ta底层,而且样品的霍尔电阻比Pt和Ta做底层要小。Ta作为Co Fe B/Pt多层膜的底层与Pt作为底层相比能够更好地和多层膜晶格匹配,并且在400℃退火后反常霍尔效应得到增强。霍尔电阻提高近80%,矫顽力达到了5.7×10~3 A·m^(–1),有望作为垂直自由层应用到磁隧道结构中。展开更多
Pseudo spin valves（SVs） exhibiting perpendicular magnetic anisotropy were prepared by magnetron sputtering. Magnetization measurements of the Co/Pt multilayers were performed to select the reference and free layers....Pseudo spin valves（SVs） exhibiting perpendicular magnetic anisotropy were prepared by magnetron sputtering. Magnetization measurements of the Co/Pt multilayers were performed to select the reference and free layers. The selection criteria are square magnetic hysteresis loops, weaker current shunting effect, and proper coercivity. The optimal reference layer and free layer are Pt（5.0 nm）/[Co（0.4 nm）/Pt（0.6 nm）]3/Co（0.4 nm）/Cu（3.0 nm）and Cu（3.0 nm）/[Co（0.4 nm）/Pt（1.5 nm）]4, respectively.The resulting pseudo SV exhibits two well-separated hysteresis loops when the field is applied perpendicular to the film plane. The minor hysteresis loop corresponding to the free layer shifts toward negative direction of the magnetic field axis, indicating ferromagnetic interlayer exchange coupling between the two magnetic layers. The coupling also enhances the coercivity（HC） of both layers. The perpendicular giant magnetoresistance（GMR） of 2.7 % is achieved with current in plane measurement. The GMR first increases when Pt seed layer is thickened, reaches a maximum of 3.0 % at 4 nm and then decreases with the further increase of thickness. But thicker Cu spacer layer always lowers the GMR of the SV.展开更多
A series of multilayers of Co36Fe46B18/SiO2 were fabricated by DC/RF magnetron sputtering,and further post-annealed in vacuum magnetic field at 200℃ for 2 h. The results show that the microstructures and electromagne...A series of multilayers of Co36Fe46B18/SiO2 were fabricated by DC/RF magnetron sputtering,and further post-annealed in vacuum magnetic field at 200℃ for 2 h. The results show that the microstructures and electromagnetic properties of Co36Fe46B18/SiO2 multilayer films can be altered by varying the thickness of CoFeB and the process of annealing. High permeability along with high magnetic loss in the GHz frequency range is achieved in the optimized discontinuous multilayer films. Both real and imaginary parts of the complex permeability are larger than 260 at 1.6 GHz for this film,and the resistivity is as high as 1.4 mΩ·cm. The discontinuous Co36Fe46B18/SiO2 multilayers are supposed to serve as the microwave absorbers and EMI shielding materials in GHz range.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
应用磁控溅射法在玻璃基片上制备了以Pt为底层的CoFeB/Ni多层膜结构样品,通过测试样品的反常霍尔效应研究多层膜的垂直磁各向异性(perpendicular magnetic anisotropy,PMA),对影响多层膜垂直磁各向异性的各因素进行了调制.实验结果表明...应用磁控溅射法在玻璃基片上制备了以Pt为底层的CoFeB/Ni多层膜结构样品,通过测试样品的反常霍尔效应研究多层膜的垂直磁各向异性(perpendicular magnetic anisotropy,PMA),对影响多层膜垂直磁各向异性的各因素进行了调制.实验结果表明,多层膜的底层厚度、周期层中各层的厚度及周期数对样品的反常霍尔效应和磁性有重要影响.通过对样品各参数的逐步调制,最终获得了具有良好PMA的CoFeB/Ni多层膜最佳样品Pt(4)/[CoFeB(0.4)/Ni(0.3)]_3/Pt(1.0).经测试计算,该样品的各向异性常数K_(eff)为2.2×10~6erg/cm^3(1 erg/cm^3=10^(-1)J/m^3),具有良好的PMA性能,样品总厚度为7.1 nm,完全满足制备垂直磁结构材料的厚度要求,可进一步研究其在器件中的集成与应用.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos.51371027 and 51331002)the National Key Scientific Research Projects of China (No.2015CB921502)the Ph.D.Programs Foundation of Ministry of Education (No.20120006130002)。
文摘The effect of ultrathin Fe layer on perpendicular magnetic anisotropy(PMA) in magnetron-sputtered Co/Pt multilayers was investigated by magnetic measurements.Magnetization hysteresis(M-H) loops and microstructures of the samples were measured by vibrating sample magnetometer(VSM) and X-ray diffraction(XRD) and highresolution transmission electron microscopy(HRTEM),respectively.It is found that the PMA is strongly dependent on the interface where Fe layer was doped.When Fe layer was doped at Co/Pt interface where Pt was deposited on Co,the PMA decreases monotonically with Fe layer thickness(tFe) increasing.However,when Fe layer was doped at Pt/Co interface where Co was deposited on Pt,the PMA shows a peak at t_(Fe)=0.1 nm.It is considered that the PMA variation is mainly due to the tuning in the electron occupation states of 3 d orbits at Fe-doped Pt/Co interface.Furthermore,the annealing stability of PMA can also be improved when Fe layer was doped at Pt/Co interface.HRTEM results demonstrate that the magnetic anisotropy evolution is mainly caused by anneal-induced interdiffusion.
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(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.
基金Supported by the National Basic Research Program of China under Grant No 2011CB921804the Beijing Key Subject Foundation of Condensed Matter Physics under Grant No 0114023
文摘The dependence of perpendicular magnetic anisotropy （PMA） on the barrier layer MgO thickness in MgO/CoFeB /Ta multilayers is investigated. The results show that the strongest PMA occurs in a small window of about 2 4nm with the increase of MgO thickness from 1-1Onto. The crystalline degree of MgO and the change of interatomic distance along the out-of-plane direction may be the main reasons for the change of PMA in these multilayers. Moreover, the roughnesses of 2- and 4-nm-thick MgO samples are 3.163 and 1.8 nm, respectively, and both the samples show PMA. These results could be used to tune the magnetic characteristic of the ultra thin CoFeB film for future applications in perpendicular magnetic devices.
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.
文摘采用磁控溅射方法在玻璃基片上制备了以Ru,Cu,Pt和Ta为底层的Co Fe B/Pt多层膜样品,研究了各底层对Co Fe B/Pt多层膜的反常霍尔效应的影响。发现Ru和Cu作为Co Fe B/Pt多层膜的底层在保持样品的垂直磁各向异性方面的作用远不如Pt和Ta底层,而且样品的霍尔电阻比Pt和Ta做底层要小。Ta作为Co Fe B/Pt多层膜的底层与Pt作为底层相比能够更好地和多层膜晶格匹配,并且在400℃退火后反常霍尔效应得到增强。霍尔电阻提高近80%,矫顽力达到了5.7×10~3 A·m^(–1),有望作为垂直自由层应用到磁隧道结构中。
基金financially supported by the National Natural Science Foundation of China (Nos. 11174020, 51331002, and 51371027)the Fundamental Research Funds for the Central Universities FRF-SD-12-011A
文摘Pseudo spin valves（SVs） exhibiting perpendicular magnetic anisotropy were prepared by magnetron sputtering. Magnetization measurements of the Co/Pt multilayers were performed to select the reference and free layers. The selection criteria are square magnetic hysteresis loops, weaker current shunting effect, and proper coercivity. The optimal reference layer and free layer are Pt（5.0 nm）/[Co（0.4 nm）/Pt（0.6 nm）]3/Co（0.4 nm）/Cu（3.0 nm）and Cu（3.0 nm）/[Co（0.4 nm）/Pt（1.5 nm）]4, respectively.The resulting pseudo SV exhibits two well-separated hysteresis loops when the field is applied perpendicular to the film plane. The minor hysteresis loop corresponding to the free layer shifts toward negative direction of the magnetic field axis, indicating ferromagnetic interlayer exchange coupling between the two magnetic layers. The coupling also enhances the coercivity（HC） of both layers. The perpendicular giant magnetoresistance（GMR） of 2.7 % is achieved with current in plane measurement. The GMR first increases when Pt seed layer is thickened, reaches a maximum of 3.0 % at 4 nm and then decreases with the further increase of thickness. But thicker Cu spacer layer always lowers the GMR of the SV.
基金Project(50771047) supported by the National Natural Science Foundation of ChinaProject(NCET-04-0702) supported by the New Century Excellent Talents in University, ChinaProject(2005ABB002) supported by the Elitist in Natural Science Foundation of Hubei Province, China
文摘A series of multilayers of Co36Fe46B18/SiO2 were fabricated by DC/RF magnetron sputtering,and further post-annealed in vacuum magnetic field at 200℃ for 2 h. The results show that the microstructures and electromagnetic properties of Co36Fe46B18/SiO2 multilayer films can be altered by varying the thickness of CoFeB and the process of annealing. High permeability along with high magnetic loss in the GHz frequency range is achieved in the optimized discontinuous multilayer films. Both real and imaginary parts of the complex permeability are larger than 260 at 1.6 GHz for this film,and the resistivity is as high as 1.4 mΩ·cm. The discontinuous Co36Fe46B18/SiO2 multilayers are supposed to serve as the microwave absorbers and EMI shielding materials in GHz range.
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.
文摘应用磁控溅射法在玻璃基片上制备了以Pt为底层的CoFeB/Ni多层膜结构样品,通过测试样品的反常霍尔效应研究多层膜的垂直磁各向异性(perpendicular magnetic anisotropy,PMA),对影响多层膜垂直磁各向异性的各因素进行了调制.实验结果表明,多层膜的底层厚度、周期层中各层的厚度及周期数对样品的反常霍尔效应和磁性有重要影响.通过对样品各参数的逐步调制,最终获得了具有良好PMA的CoFeB/Ni多层膜最佳样品Pt(4)/[CoFeB(0.4)/Ni(0.3)]_3/Pt(1.0).经测试计算,该样品的各向异性常数K_(eff)为2.2×10~6erg/cm^3(1 erg/cm^3=10^(-1)J/m^3),具有良好的PMA性能,样品总厚度为7.1 nm,完全满足制备垂直磁结构材料的厚度要求,可进一步研究其在器件中的集成与应用.
