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
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
利用倾斜溅射的方法制备了非晶Co Fe B磁性薄膜,研究了倾斜溅射对非晶Co Fe B磁性薄膜条纹磁畴结构、面内静态磁各向异性、面内转动磁各向异性、垂直磁各向异性的影响规律。结果表明,倾斜溅射可以有效地降低Co Fe B非晶薄膜条纹磁畴结...利用倾斜溅射的方法制备了非晶Co Fe B磁性薄膜,研究了倾斜溅射对非晶Co Fe B磁性薄膜条纹磁畴结构、面内静态磁各向异性、面内转动磁各向异性、垂直磁各向异性的影响规律。结果表明,倾斜溅射可以有效地降低Co Fe B非晶薄膜条纹磁畴结构出现的临界厚度,无倾斜溅射时,Co Fe B薄膜出现条纹磁畴结构的临界厚度大于240 nm,倾斜溅射时,出现条纹磁畴结构的临界厚度小于240 nm。磁性测试结果表明,对于具有条纹磁畴结构的Co Fe B薄膜,倾斜溅射不仅可以提高磁性薄膜的面内静态磁各向异性的强度,同时还可以增强面内转动磁各向异性与垂直磁各向异性的强度。随着倾斜溅射角度的逐渐增大,磁各向异性的强度均呈现增大的趋势。XRD和TEM观测结果证明,Co Fe B薄膜趋于非晶结构,同时,SEM观察结果表明,Co Fe B薄膜虽然不存在长程有序的晶体结构,但依然可以形成柱状结构,由于倾斜溅射技术,形成的柱状结构呈倾斜状态,从而增强了薄膜的垂直磁各向异性,导致条纹磁畴结构的出现。展开更多
Electroless CoFeB films with good soft magnetic properties were fabricated on polyester plastic substrate from sodium tartarate as a complexing agent.The plating rate of electroless CoFeB films is a function of concen...Electroless CoFeB films with good soft magnetic properties were fabricated on polyester plastic substrate from sodium tartarate as a complexing agent.The plating rate of electroless CoFeB films is a function of concentration of sodium tetrahydroborate,pH of the plating bath,plating temperature and the metallic ratio.The estimated regression coefficient b0-b3 confidence interval,residual error r and confidence interval rint were confirmed by a computer program.The optimal composition of the plating bath was obtained and the dynamic electromagnetic parameters of films were measured in the 2-10 GHz range.At 2 GHz,the μ＇,μ″ of the electroless CoFeB films were 304 and 76.6,respectively,as the concentration of reducer is 1 g/L.Magnetic hysteresis loop of the deposited CoFeB films show a remanence close to the saturation magnetization and coercivity of about 55.7-127.4 A/m.The loops along the hard axis display low anisotropic field Hk of 2 388-3 582 A/m.展开更多
聚焦离子束系统(focus ion beam,FIB)作为一种成熟的材料加工技术,在磁性材料的加工中得到广泛应用。然而,在利用FIB对磁性材料的加工过程中,难免会因为离子的辐照对样品产生影响。本文以CoFeB薄膜为研究对象,研究辐照强度对样品磁性质...聚焦离子束系统(focus ion beam,FIB)作为一种成熟的材料加工技术,在磁性材料的加工中得到广泛应用。然而,在利用FIB对磁性材料的加工过程中,难免会因为离子的辐照对样品产生影响。本文以CoFeB薄膜为研究对象,研究辐照强度对样品磁性质的影响。对于利用离子束辐照来调控薄膜性质具有指导意义。展开更多
The kinetics equation of deposition rate was implemented to help explain some of the mechanisms responsible for structures observed during the deposition of CoFeB films on poly-ester plastic. The plating rate of elect...The kinetics equation of deposition rate was implemented to help explain some of the mechanisms responsible for structures observed during the deposition of CoFeB films on poly-ester plastic. The plating rate of electroless CoFeB films is a function of concentration of sodium tetrahydroborate, pH of the plating bath, plating temperature and the metallic ratio. The estimated regression coefficient, confidence interval, residual error and confidence interval were confirmed by computer program. The optimal composition of the plating bath was obtained and the dynamic electromagnetic parameters of films were measured in the 2-10 GHz range. At 2 GHz, the permeability, magnetic loss of the electroless CoFeB films were 304,76.6 respectively as the concentration of reducer is 1 g·L^-1.展开更多
To study the influence of CoFeB/MgO interface on tunneling magnetoresistance （TMR）, different structures of magnetic tunnel junctions （MTJs） are successfully prepared by the magnetron sputtering technique and char...To study the influence of CoFeB/MgO interface on tunneling magnetoresistance （TMR）, different structures of magnetic tunnel junctions （MTJs） are successfully prepared by the magnetron sputtering technique and characterized by atomic force microscopy, a physical property measurement system, x-ray photoelectron spectroscopy, and transmission electron microscopy. The experimental results show that TMR of the CoFeB/Mg/MgO/CoFeB structure is evidently improved in comparison with the CoFeB/MgO/CoFeB structure because the inserted Mg layer prevents Fe-oxide formation at the CoFeB/MgO interface, which occurs in CoFeB/MgO/CoFeB MTJs. The inherent properties of the CoFeB/MgO/CoFeB, CoFeB/Fe-oxide/MgO/CoFeB and CoFeB/Mg/MgO/CoFeB MTJs are simulated by using the theories of density functions and non-equilibrium Green functions. The simulated results demonstrate that TMR of CoFeB/Fe-oxide/MgO/CoFeB MTJs is severely decreased and is only half the value of the CoFeB/Mg/MgO/CoFeB MTJs. Based on the experimental results and theoretical analysis, it is believed that in CoFeB/MgO/CoFeB MTJs, the interface oxidation of the CoFeB layer is the main reason to cause a remarkable reduction of TMR, and the inserted Mg layer may play an important role in protecting Fe atoms from oxidation, and then increasing TMR.展开更多
An obvious weak localization correction to anomalous Hall conductance（AHC） in very thin CoFeB film is reported.We find that both the weak localization to AHC and the mechanism of the anomalous Hall effect are relate...An obvious weak localization correction to anomalous Hall conductance（AHC） in very thin CoFeB film is reported.We find that both the weak localization to AHC and the mechanism of the anomalous Hall effect are related to the CoFeB thickness.When the film is thicker than 3 nm,the side jump mechanism dominates and the weak locaUzation to AHC vanishes.For very thin CoFeB films,both the side jump and skew scattering mechanisms contribute to the anomalous Hall effect,and the weak localization correction to AHC is observed.展开更多
Exchange coupling across the interface between a ferromagnetic(FM)layer and an antiferromagnetic(AFM)or another FM layer may induce a unidirectional magnetic anisotropy and/or a uniaxial magnetic anisotropy,which has ...Exchange coupling across the interface between a ferromagnetic(FM)layer and an antiferromagnetic(AFM)or another FM layer may induce a unidirectional magnetic anisotropy and/or a uniaxial magnetic anisotropy,which has been extensively studied due to the important application in magnetic materials and devices.In this work,we observed a fourfold magnetic anisotropy in amorphous Co Fe B layer when exchange coupling to an adjacent Fe Rh layer which is epitaxially grown on an SrTiO_(3)(001)substrate.As the temperature rises from 300 K to 400 K,Fe Rh film undergoes a phase transition from AFM to FM phase,the induced fourfold magnetic anisotropy in the Co Fe B layer switches the orientation from the Fe Rh<110>to Fe Rh<100>directions and the strength is obviously reduced.In addition,the effective magnetic damping as well as the two-magnon scattering of the Co Fe B/Fe Rh bilayer also remarkably increase with the occurrence of magnetic phase transition of Fe Rh.No exchange bias is observed in the bilayer even when Fe Rh is in the nominal AFM state,which is probably because the residual FM Fe Rh moments located at the interface can well separate the exchange coupling between the below pinned Fe Rh moments and the Co Fe B moments.展开更多
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.
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。
文摘利用倾斜溅射的方法制备了非晶Co Fe B磁性薄膜,研究了倾斜溅射对非晶Co Fe B磁性薄膜条纹磁畴结构、面内静态磁各向异性、面内转动磁各向异性、垂直磁各向异性的影响规律。结果表明,倾斜溅射可以有效地降低Co Fe B非晶薄膜条纹磁畴结构出现的临界厚度,无倾斜溅射时,Co Fe B薄膜出现条纹磁畴结构的临界厚度大于240 nm,倾斜溅射时,出现条纹磁畴结构的临界厚度小于240 nm。磁性测试结果表明,对于具有条纹磁畴结构的Co Fe B薄膜,倾斜溅射不仅可以提高磁性薄膜的面内静态磁各向异性的强度,同时还可以增强面内转动磁各向异性与垂直磁各向异性的强度。随着倾斜溅射角度的逐渐增大,磁各向异性的强度均呈现增大的趋势。XRD和TEM观测结果证明,Co Fe B薄膜趋于非晶结构,同时,SEM观察结果表明,Co Fe B薄膜虽然不存在长程有序的晶体结构,但依然可以形成柱状结构,由于倾斜溅射技术,形成的柱状结构呈倾斜状态,从而增强了薄膜的垂直磁各向异性,导致条纹磁畴结构的出现。
文摘Electroless CoFeB films with good soft magnetic properties were fabricated on polyester plastic substrate from sodium tartarate as a complexing agent.The plating rate of electroless CoFeB films is a function of concentration of sodium tetrahydroborate,pH of the plating bath,plating temperature and the metallic ratio.The estimated regression coefficient b0-b3 confidence interval,residual error r and confidence interval rint were confirmed by a computer program.The optimal composition of the plating bath was obtained and the dynamic electromagnetic parameters of films were measured in the 2-10 GHz range.At 2 GHz,the μ＇,μ″ of the electroless CoFeB films were 304 and 76.6,respectively,as the concentration of reducer is 1 g/L.Magnetic hysteresis loop of the deposited CoFeB films show a remanence close to the saturation magnetization and coercivity of about 55.7-127.4 A/m.The loops along the hard axis display low anisotropic field Hk of 2 388-3 582 A/m.
文摘聚焦离子束系统(focus ion beam,FIB)作为一种成熟的材料加工技术,在磁性材料的加工中得到广泛应用。然而,在利用FIB对磁性材料的加工过程中,难免会因为离子的辐照对样品产生影响。本文以CoFeB薄膜为研究对象,研究辐照强度对样品磁性质的影响。对于利用离子束辐照来调控薄膜性质具有指导意义。
基金the National Natural Science Foundation of China(No.50371029
文摘The kinetics equation of deposition rate was implemented to help explain some of the mechanisms responsible for structures observed during the deposition of CoFeB films on poly-ester plastic. The plating rate of electroless CoFeB films is a function of concentration of sodium tetrahydroborate, pH of the plating bath, plating temperature and the metallic ratio. The estimated regression coefficient, confidence interval, residual error and confidence interval were confirmed by computer program. The optimal composition of the plating bath was obtained and the dynamic electromagnetic parameters of films were measured in the 2-10 GHz range. At 2 GHz, the permeability, magnetic loss of the electroless CoFeB films were 304,76.6 respectively as the concentration of reducer is 1 g·L^-1.
基金Supported by the National Defense Advance Research Foundation under Grant No 9140A08XXXXXX0DZ106the Basic Research Program of Ministry of Education of China under Grant No JY10000925005+2 种基金the Scientific Research Program Funded by Shaanxi Provincial Education Department under Grant No 11JK0912the Scientific Research Foundation of Xi'an University of Science and Technology under Grant No 2010011the Doctoral Research Startup Fund of Xi'an University of Science and Technology under Grant No 2010QDJ029
文摘To study the influence of CoFeB/MgO interface on tunneling magnetoresistance （TMR）, different structures of magnetic tunnel junctions （MTJs） are successfully prepared by the magnetron sputtering technique and characterized by atomic force microscopy, a physical property measurement system, x-ray photoelectron spectroscopy, and transmission electron microscopy. The experimental results show that TMR of the CoFeB/Mg/MgO/CoFeB structure is evidently improved in comparison with the CoFeB/MgO/CoFeB structure because the inserted Mg layer prevents Fe-oxide formation at the CoFeB/MgO interface, which occurs in CoFeB/MgO/CoFeB MTJs. The inherent properties of the CoFeB/MgO/CoFeB, CoFeB/Fe-oxide/MgO/CoFeB and CoFeB/Mg/MgO/CoFeB MTJs are simulated by using the theories of density functions and non-equilibrium Green functions. The simulated results demonstrate that TMR of CoFeB/Fe-oxide/MgO/CoFeB MTJs is severely decreased and is only half the value of the CoFeB/Mg/MgO/CoFeB MTJs. Based on the experimental results and theoretical analysis, it is believed that in CoFeB/MgO/CoFeB MTJs, the interface oxidation of the CoFeB layer is the main reason to cause a remarkable reduction of TMR, and the inserted Mg layer may play an important role in protecting Fe atoms from oxidation, and then increasing TMR.
基金supported by the National Basic Research Program of China(Grant No.2012CB933102)the National Natural Science Foundation of China(Grant Nos.11079052,11174354,and 51172080)
文摘An obvious weak localization correction to anomalous Hall conductance（AHC） in very thin CoFeB film is reported.We find that both the weak localization to AHC and the mechanism of the anomalous Hall effect are related to the CoFeB thickness.When the film is thicker than 3 nm,the side jump mechanism dominates and the weak locaUzation to AHC vanishes.For very thin CoFeB films,both the side jump and skew scattering mechanisms contribute to the anomalous Hall effect,and the weak localization correction to AHC is observed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11874150,51871233,and 12174103)the Natural Science Foundation of Shanghai(Grant Nos.21ZR1420500 and 21JC1402300)。
文摘Exchange coupling across the interface between a ferromagnetic(FM)layer and an antiferromagnetic(AFM)or another FM layer may induce a unidirectional magnetic anisotropy and/or a uniaxial magnetic anisotropy,which has been extensively studied due to the important application in magnetic materials and devices.In this work,we observed a fourfold magnetic anisotropy in amorphous Co Fe B layer when exchange coupling to an adjacent Fe Rh layer which is epitaxially grown on an SrTiO_(3)(001)substrate.As the temperature rises from 300 K to 400 K,Fe Rh film undergoes a phase transition from AFM to FM phase,the induced fourfold magnetic anisotropy in the Co Fe B layer switches the orientation from the Fe Rh<110>to Fe Rh<100>directions and the strength is obviously reduced.In addition,the effective magnetic damping as well as the two-magnon scattering of the Co Fe B/Fe Rh bilayer also remarkably increase with the occurrence of magnetic phase transition of Fe Rh.No exchange bias is observed in the bilayer even when Fe Rh is in the nominal AFM state,which is probably because the residual FM Fe Rh moments located at the interface can well separate the exchange coupling between the below pinned Fe Rh moments and the Co Fe B moments.
