Perpendicular magnetic anisotropy of Co_(85)Cr_(50)/Pt multilayers

The CoCr/Pt bilayers and (CoCr/Pt)20 multilayers with Pt underlayer were prepared by DC magnetron sputtering. The effects of prepared condition on perpendicular magnetic anisotropy were investigated. The results show that the thickness of Pt under-layer has a great effect on the microstructure and perpendicular magnetic anisotropy of CoCr/Pt bilayers and (CoCr/Pt)20 multilayers. When the thickness of Pt underlayer increases, Pt(111) and CoCr(002) peaks of both CoCr/Pt bilayers and (CoCr/Pt)20 multilayers increase and the bilayer periodicity of the multilayers is improved. The effective magnetic anisotropy of (CoCr/Pt)20 multilayers with Pt underlayer was much larger than that of CoCr/Pt bilayers. The (CoCr/Pt)20 multilayers has a stronger perpendicular magnetic anisotropy than that of CoCr/Pt bilayers. This is ascribed to the interface magnetic anisotropy of the multilayers.     

Perpendicular exchange bias of (Pt/Co)_n/FeMn multilayers

(Pt/Co)n/FeMn multilayers with perpendicular anisotropy (PA) were prepared by magnetron sputtering with Pt as the buffer layer and the capping layer. The dependence of perpendicular exchange bias (PEB), Hex, on the thickness of the FeMn antiferromagnet (AFM) layer is similar to that of in-plane exchange bias. The value of Hex for the (Pt/Co)3/FeMn multilayer reaches 22.3 kA/m. A thin Pt spacer was inserted between the Co/FeMn interface to enhance PEB. The PEB reaches the largest at 39.8 kA/m when the thickness of the Pt spacer is 0.4 nm.     

Perpendicular exchange bias of （Pt/Co）n/FeMn multilayers

(Pt/Co)n/FeMn multilayers with perpendicular anisotropy (PA) were prepared by magnetron sputtering with Pt as the buffer layer and the capping layer. The dependence of perpendicular exchange bias (PEB), Hex, on the thickness of the FeMn antiferromagnet (AFM) layer is similar to that of in-plane exchange bias. The value of Hex for the (Pt/Co)3/FeMn multilayer reaches 22.3 kA/m. A thin Pt spacer was inserted between the Co/FeMn interface to enhance PEB. The PEB reaches the largest at 39.8 kA/m when the thickness of the Pt spacer is 0.4 nm.     

Dependence of domain wall structures on repetition n in[Pt（0.5 nm）/Co（0.4 nm）]n/NiO（1.1 nm）/[Co（0.4 nm）/Pt（0.5 nm）]n multilayers

The magnetic force microscopy and a sample vibrating magnetometer have been used to investigate the domain structure in two antiferromagnetically coupled Co/Pt multilayers.In the antiferromagnetic coupled[Pt(0.5 nm)/Co(0.4 nm)]_n/NiO(1.1 nm)/[Co(0.4 nm)/Pt(0.5 nm)]_n multilayers with perpendicular anisotropy,the antiferromagnetic interlayer coupling strength increases linearly with the repetition number n in Co/Pt multilayers.In demagnetized states,relatively shifted domain walls in the two Co/Pt multila...     

Microstructure and magnetic properties of FePt/MgO multilayers deposited by RF magnetron sputtering

FePt (50 nm) and [FePt(a nm)/MgO(b nm)]5/glass (a=1, 2, 3; b=1, 2, 3) films were prepared by radio frequency (RF) magnetron sputtering technique, and then were annealed at 600°C for 30 min. The effect of MgO layer thickness on the structures and magnetic properties of the FePt/MgO multilayers was investigated. The coercivities and inter-grain interactions of the FePt/MgO films were decreased, yet the degree of (001) texturing drastically increased with the increase in MgO layer thickness when the FePt layer thickness was fixed. Thus, the FePt/MgO films with appropriate coercivities, high perpendicular anisotropy, and weak in-ter-grain interactions were obtained by controlling the MgO layer thickness. Overall, these results indicate that the FePt/MgO nanos-tructured films are promising candidates for future high-density perpendicular recording media.     

Microstructures and magnetic properties of [SiO2/FePt]5/Ag thin films

[SiO2/FePt]5/Ag thin films were deposited by RF magnetron sputtering on the glass substrates and post annealing at 550 ℃ for 30 min in vacuum. Vibrating sample magnetometer and X-ray diffraction analyser were applied to study the magnetic properties and microstructures of the films. The results show that without Ag underlayer [SiO2/FePt]5 films deposited onto the glass are FCC disordered; with the addition of Ag underlayer [SiO]FePt]5/Ag films are changed into L10 and （111） mixed texture. The variation of the SiO2 nonmagnetic layer thickness in [SiO2/FePt]5/Ag films indicates that SiO2-doping plays an important role in improving the order parameter and the perpendicular magnetic anisotropy, and reducing the grain size and intergrain interactions. By controlling SiO2 thickness the highly perpendicular magnetic anisotropy can be obtained in the [SiO2 （0.6 nm）/FePt （3 nm）]5/Ag （50 nm） films and highly （001）-oriented films can be obtained in the [SiO2 （2 nm）/FePt （3 nm）]5/Ag （50 nm） films.     

Influence of Si buffer layer on the giant magnetoresistance effect in Co/Cu/Co sandwiches

The Co/Cu/Co sandwiches with a semiconductor Si buffer layer were prepared by high vacuum electron-beam evaporation. The influence of the Si buffer layer with different thickness on the giant magnetoresistance (GMR) effect in the Co/Cu/Co sandwiches was investigated. It was found that the GMR showed an obvious anisotropy when the thickness of Si buffer layer was larger than or equal to 0.9 nm, and that the GMR was basically isotropic with an Si buffer layer thinner than 0.9 nm. The anisotropic behavior of GMR can be ascribed to the in-plane magnetic anisotropy in the sandwiches. Due to the interdiffusion at the Si buffer/Co interface, a Co2Si interface layer with a good (301) texture formed and induced the in-plane magnetic anisotropy in the sandwiches. The dependence of the crystalline texture of the sandwiches on the thickness of Si buffer layer was also studied.     

Structures and properties of [CoPt/Ag]_n multilayer films

In recent years there has been considerable interest in atomically ordered L10-CoPtfilms as potential materials for ultrahigh density magnetic recording (UDMR) media[1].The L10 phase CoPt alloy has high anisotropy constant of 107—108 erg/cm3, which is ofcrucial importance for UDMR media with a small grain size below 10 nm, because highmagnetocrystalline anisotropy is needed to create a barrier to thermally activatedswitching of the magnetization[2, . The as-deposited CoPt film with equi…     

Effects of Nd substitution on magnetic and magneto-optical properties of TbCo/Cr films

NdTbCo/Cr amorphous films with high perpendicular magnetic anisotropy were prepared onto glass substrates by rf magnetron sputtering. The effects of Nd substitution on the magnetic and magneto-optical properties of TbCo/Cr films were investigated. It was found that partial Tb substitution by Nd would increase the saturation magnetization and the Kerr rotation angle, change the temperature dependence of magneto-optical characteristics. These results can be explained by the ferrimagnetic structure of the rare earth-transition metal alloy. When the magnetic layer composition was （Nd0.265Tb0.735）31Co69, a saturation magnetization of 247 emu/cm^3 and a coercivity of 3.8 kOe at room temperature could be obtained.     

Struetural and Magnetic Properties of Electrodeposited Ni70Fe30 Nanowire Array

Ordered Ni70Fe30 nanowire array was fabricated in a porous alumina template by altemating current electrodeDositiOn.The structural and magnetic properties of the as-obtained nanowire array were investigated by SEM,TEM,XRD,EDS and VSM.The results indicate that the as-obtained Ni70Fe30 nanowires exhibit a diameter of about 69.9 nm and aspect ratio of more than 60.Meanwhile,a preferred orientation[110]of bcc lattice was observed.The as-obtained nanowire array has an obvious magnetic anisotropy,of which the easy direction is perpendicular to the surface of the array.Moreover,after annealed,the Ni70Fe30 nanowire array exhibits an enhanced magnetic anisotropy.     

阶段张应力退火Fe基合金的磁各向异性

为完善张应力退火感生磁各向异性的结构机理,采用阶段张应力退火(tensile stress annealing at different phases,TSADP)方法制备了系列Fe_(73.5)Cu_1 Nb_3 Si_(13.5)B_9纳米晶合金带,使用HP4294A型阻抗仪和P47H型原子力显微镜(atomic force microscope,AFM)分别检测了样品的纵向驱动巨磁阻抗(longitudinal driven giant magnetoimpedance,LDGMI)效应及全程张应力退火样品(S_5)横断面介观结构和磁结构.结果表明:保温阶段加载张应力退火样品(S_3)中感生的横向磁各向异性(H_k)最大;横断面有与外加张应力方向成一定夹角α(0°≤α≤90°)的颗粒团聚现象存在且其磁结构为片状畴.并提出了阶段张应力退火颗粒团聚模型,认为阶段张应力退火感生横向磁各向异性可能起源于参与方向性团聚颗粒间的磁交换耦合效应.     

Structures and properties of [CoPt/Ag]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> multilayer fims

The magnetic properties and structures of [CoPt/Ag] _n , multilayer films deposited by DC magnetron sputtering have been studied. During the deposited process, two kinds of deposited sequences, that is Ag layer (FDAG) first deposited or CoPt layer (FDCP) first deposited, have been chosen. The results show that the microstructures and coercivities were strongly influenced by the deposited sequence and the thickness of films. The coercivities of [Ag/CoPt] _n with FDAG are obviously higher than those of [CoPt/Ag] _n with FDCP. Especially, when the thickness of films is 8 nm, the difference of coercivities between the FDAG film and the FDCP film is the largest. It is possibly because Ag plays a role of underlayer in FDAG multilayers, which can induce both the transformation from fcc to fct and the oriented growth along c-axis. In addition, δM curves reveal that the [CoPt/Ag]₈ multilayer, film has a lower intergrain interaction than the CoPt/Ag bilayer film.     

The effect of interface roughness on the perpendicular exchange bias of NiO/CoPt/Pt stacking structure

An orthogonal coupling structure of Ni O/Co Pt/Pt/glass with perpendicular exchange bias effect has been prepared. The exchange bias is found to be strongly dependent on the interface roughness between Ni O and Co Pt layer. The conventional inverse proportionality of the exchange bias field with the ferromagnetic thickness is not applicable to this top-pinned stacking structure.Moreover, an anomalous ferromagnetic thickness dependence of blocking temperature is also observed. A simulation on the basis of a spin configuration model with defects at the interface agrees well with the experimental observations. These findings suggest considerable contribution of the interface roughness to the perpendicular exchange bias.     

PREPARATION AND MAGNETORHEOLOGICAL PROPERTIES OF AQUEOUS SUSPENSION BASED ON EMULSION DROPLETS CONTAINING Fe_3O_4 NANOPARTICLES

The Fe3O4 nanoparticles with mean size of 10 nm were prepared by chemical common precipitation . The factors influencing the size and shape of Fe3O4 nanoparticles such as the adding rate of NaOII to the mixed solution and the final pH of the solution were studied . The Fe3O4 based magnetorheological(MR) fluid was formed by adding surfactant . The rheological properties of this MR fluid were studied when the magnetic fields with different direction are applied. It has been found that the MR fluid has the magnetic anisotropy.     

Structural and magnetic properties of electrodeposited Ni<Subscript>70</Subscript>Fe<Subscript>30</Subscript> nanowire array

Ordered Ni70Fe30 nanowire array was fabricated in a porous alumina template by alternating current electrodeposition. The structural and magnetic properties of the as-obtained nanowire array were investigated by SEM, TEM, XRD, EDS and VSM. The results indicate that the as-obtained Ni70Fe30 nanowires exhibit a diameter of about 69.9 nm and aspect ratio of more than 60. Meanwhile, a preferred orientation [110] of bcc lattice was observed. The as-obtained nanowire array has an obvious magnetic anisotropy, of which the easy direction is perpendicular to the surface of the array. Moreover, after annealed, the Ni70Fe30 nanowire array exhibits an enhanced magnetic anisotropy.     

纳米复合Nd2Fe14B/α Fe磁体中晶粒的随机各向异性

以Nd2Fe14B/α Fe为例，研究了球状纳米晶粒尺寸对复合磁性材料有效随机各向异性的影响. 结果表明，材料的有效随机各向异性常数〈Keff〉随软磁性晶粒尺寸Ds的增加而减小，随硬磁性晶粒尺寸Dh的增加而增大.要使复合磁性材料获得较大的各向异性(矫顽力),Ds应尽量减小(10?nm左右), Dh尽量增大.为使材料具有高的磁能积,Dh应大于10?nm, Ds在10?nm左右. 关键词：有效随机各向异性；纳米晶粒；纳米复合材料；交换耦合相互作用     

快速热处理的[Fe/Pt]n薄膜的结构和磁性

采用直流磁控溅射方法在Si基片上制备[Fe/Pt]_n薄膜,利用X射线荧光光谱仪(XRF)、X射线衍射仪(XRD)和振动样品磁强计(VSM)分析薄膜的组分、结构和磁性。研究结果表明：[Fe/Pt]_n薄膜经过600 ℃快速热处理,得到了L1₀-FePt薄膜。对于[Fe (x nm)/Pt (0.5 nm)]_n薄膜,当Fe层厚度为0.7 nm时,薄膜的有序度最大,平行膜面和垂直膜面的矫顽力均最高;对于不同调制周期的[Fe/Pt]_n薄膜,有序度随调制周期先增大后减小,平行膜面的矫顽力均高于垂直膜面的矫顽力,当调制周期为2.4 nm时,薄膜平行膜面的矫顽力最大。     

场致排列CrO2/Polystyrence复合材料结构及磁性分析

研究了CrO2/Polystyrence（聚苯乙烯简称PS）的场致排列复合材料的结构与磁性.通过对场致排列CrO2/PS复合样品与随机样品XRD的比较分析显示复合排列样品具有明显的各向异性特征,PS的加入并没有改变晶体的结构.磁滞洄线分析显示磁场平行于样品的易磁化轴时样品的磁矩很容易饱且剩磁较大,垂直时样品的磁矩不容易饱且剩磁较小.     

不同因素对铁磁性薄膜中表面自旋波频率的影响

为了了解铁磁性薄膜中表面自旋波的物理性质,采用量子格林函数方法研究了铁磁性薄膜中表面自旋波的频率,分析了温度、外磁场、表面交换耦合、表面各向异性、薄膜厚度和波矢对表面自旋波频率的影响.结果表明,声学和光学表面自旋波的频率随温度的升高而减小.随着外磁场、表面交换耦合、表面各向异性和波矢的增加,声学和光学表面自旋波的频率随之增加.随着原子层数的减小,声学和光学表面自旋波频率增大.但当薄膜的原子层数大于5时,薄膜厚度对声学和光学表面自旋波频率的影响很小.     

Anisotropic characteristic in HDDR Nd_(13)Fe_(80)B_7

The function of disproportionation and desorption stages of hydrogenation-disproportionation-desorption-recombination (HDDR) process in the formation of magnetic anisotropy was studied. The results showed that degree of anisotropy (DOA) of Nd13Fe80B7induced by appropriate HDDR process is comparable with that of Nd13Fe80-xB7Mx(M=Co, Zr or Ga), however, the moderate coercive force of Nd13Fe80B7 magnetic powder led to an undesirable (BH)max of 104 kJ/m3 in bonded magnet. Experiments demonstrated that a relatively short disproportionation time, combined with a high desorption temperature and slow desorption rate, during HDDR process is beneficial to anisotropy attainment, but HDDR Nd13Fe80B7 magnetic powder becomes isotropic if the disproportionation time is longer than a certain period. This phenomenon strongly indicated that the origin of anisotropy in NdFeB-type HDDR material is contributed by disproportionation stage. XRD (X-ray Diffraction) analysis and TEM (Transmission Electron Microscope) observatio