Sm-Fe和Sm-Co非晶态合金薄膜的高场热磁效应

本文研究了Sm_xT_1-x(T=Fe,Co)非晶态薄膜的磁化强度σ与温度T的关系。发现在磁场H=7T下,对Sm_xCo_1-x样品(x=0.46,0.48,0.54,0.65)的升温过程测得的σ(T)曲线上有极大值,它对应的温度都在25—28K范围内,与成分关系不大。非晶态Sm_xFe_1-x(x=0.46,0.73)的结果与之不同,极大值对应的温度与成分有关。对上述样品,还发现在T≈6K附近σ(T)有极小值(和陡变),在近室温端,出现σ(T)下降缓慢的“拖尾巴”现象。我们认为,Sm-Co非晶态薄膜表现的高场热磁效应可能起源于Sm原子磁矩对磁化的贡献不可忽略,作用在Sm原子上的局域无规各向异性很强;这种各向异性在20—30K变化较大。而Sm-Fe薄膜的高场热磁效应可能起源于Fe原子磁矩的分散。σ(T)在6K附近的极小值(和陡变)及其在室温端变化缓慢的原因,可能是合金成分的涨落所致。 关键词：     

非晶Nd-Fe薄膜的磁性

在用闪蒸法制备的非晶Nd_xFe_1-x薄膜中Nd的原子磁矩呈散铁磁性排列,其有效磁矩随Nd含量增加而减小。磁有序温度T_c的值与外场和测量方法有关,表明了具有不同磁有序温度的磁性原子团的存在。交换交互作用,而不是自发磁化强度,明显地受制备条件的影响。 关键词：     

化合物SmCo5的电子结构、自旋和轨道磁矩及其交换作用分析

用自旋极化的MS-Xα方法研究了稀土-过渡族化合物SmCo5₅的电子态密度、自 旋能级劈裂及原子磁矩.研究结果显示，由于化合物中Sm-Co间的轨道杂化效应，使Sm原子原来的5d00空轨道上占据了少量5d电子.由于Co(3d)-Sm(5d)电子间的直接交换作用，导致了Sm-Co间的磁性交换耦合，这是化合物中形成Sm-Co铁磁性长程序的一个重要原因.在SmCo5_{5化合物中存在6个能级呈现负交换耦合，导致了SmCo55化 关键词： 电子结构 自旋极化 原子磁矩 交换耦合}     

非平衡Fe-Pd合金的矫顽力与磁致伸缩

通过测量非平衡Fe_1-xPd_x合金的矫顽力H_c与饱和磁致伸缩系数λ_s,随合金成分的变化,发现H_c随x增加而减小,而λ_s随x增加而增大。认为晶粒尺寸减小引起的平均各向异性的降低可能是H_c减小的原因。退火温度T_a>600K时,由于具有高磁晶各向异性的有序FePd相的分离析出,矫顽力H_c随T_a升 关键词：     

强磁场下Sm-Fe薄膜不同晶态组织演化及磁性能调控

针对Sm-Fe薄膜的不同晶态组织演化和磁性能调控问题,采用分子束气相沉积方法制备Sm-Fe薄膜时,通过改变Sm含量、膜厚和强磁场来调节薄膜的晶态和磁性能.结果表明,Sm含量可以调节Sm-Fe薄膜的晶态组织演化,而晶态组织的演化和强磁场对磁性能有显著影响.Sm-Fe薄膜在Sm原子比为5.8%时是体心立方晶态组织,在Sm含量为33.0%时为非晶态组织,而膜厚和强磁场不会影响薄膜的晶态组织.非晶态薄膜的表面粗糙度和表面颗粒尺寸都比晶态薄膜的小,施加6 T强磁场会使表面颗粒尺寸增大,而表面粗糙度降低.非晶态薄膜的饱和磁化强度M_s比晶态薄膜的M_s(1466 emu/cm~3,1 emu/cm~3=4π×10-10T)低约47.6%,施加6 T强磁场使非晶态和晶态薄膜的M_s均降低约50%.Sm-Fe薄膜的矫顽力H_c在6—130 Oe(1 Oe=103/(4π)A/m)之间,其中,非晶态薄膜的H_c比晶态薄膜的H_c大.施加6 T强磁场使晶态薄膜的H_c增大,而使非晶态薄膜的H_c减小,最高可以减少95%.结果表明含量和强磁场可以用于调控Sm-Fe薄膜的晶态和磁性能.     

非晶态(Fe1-xVx)84B16合金的磁性和电性

用单辊急冷法制备了非晶态(Fe_1-xV_x)₈₄B₁₆(x=0,0.02,0.04,0.06,0.10)合金的薄带,分别用磁天平和四端引线法测量了饱和磁化强度和高温电阻率的温度关系。得到平均每个磁性原子的磁矩随V含量的增加近似线性下降,计算出每个Fe原子和每个V原子的平均磁矩分别为2.08μ_B和-5.08μ_B。居里温度T_c从x=0时的622K下降到x=0.10时的478K。利用自旋波激发公式:σ(T)=σ(0)(1-BT^* 关键词：     

非晶态合金Pr-Co薄膜的磁性

本文研究了非晶态Pr_xCo_1-x薄膜合金的磁化强度与温度和磁场的关系。得到非晶态合金Pr-Co中存在有两个磁相的结论。这可能是由于局域化学短程序涨落造成的相分离,通过对磁化强度-温度曲线拟合,得到了这两相的相变温度。另外通过对合金的饱和磁矩与成份的关系研究,分别得到Pr原子的有效原子磁矩与成份的关系,以及Co原子在x=0时的有效原子磁矩。 关键词：     

a-C:H薄膜的光致发光

利用射频辉光放电法沉积a-C:H薄膜,研究不同测量温度、不同退火温度光致发光光谱的变化,以及光致发光光谱随光子能量的变化,实验表明:随着测量温度的升高发光效率降低,用非晶碳网络的二相系统模型对这些结果作了解释。另外,光致发光光谱也随着激发光能量的不同而变化,当激发光能量接近光学带隙E_opt时,发光强度最高。 关键词：     

XAFS研究Ni-P和Ni-Ce-P超细非晶合金的退火晶化

采用原子配位分布函数为Gaussian函数Ｐ_G和指数函数P_E直积的非 对称模型进行拟合计算,XAFS定量地研究化学还原法制备的Ni-P和Ni-Ce-P超细非晶合金大 无序度体系中Ni原子的局域环境结构随退火温度升高而产生的变化.结果表明Ni-P和Ni-Ce-P 原样的Ni-Ni配位的平均键长Ｒ_j、配位数N、热无序度σ_T、结构无 序度σ_S分别为0271nm,100,00060nm,0028n 关键词： XAFS Ni-P Ni-Ce-P 超细非晶合金 局域结构     

La掺杂BaSnO3薄膜的低温电输运性质

利用射频磁控溅射技术在MgO(001)单晶基片上沉积了一系列Ba_0.94La_0.06SnO₃薄膜,并对薄膜的结构和电输运性质进行了系统研究.所有薄膜均表现出简并半导体(金属)导电特性:在T>T_min的高温区(T_min为电阻最小值对应的温度),薄膜的电阻率随温度的升高而升高,并且与温度的平方呈线性关系.在T min的低温区域,薄膜的电阻率随温度降低而上升,并且电阻率随lnT呈线性变化,均匀无序系统中的电子-电子相互作用、弱局域效应以及Kondo效应均不能解释这种现象.经过定量分析,发现电阻率在低温下lnT的依赖关系源于颗粒间电子的库仑相互作用.同时,在Ba_0.94La_0.06SnO₃薄膜中也观察到霍尔系数R_H与lnT呈线性关系,并且该线性关系也定量的符合金属颗粒体系中库仑相互作用的理论.薄膜断面高分辨透射电子显微镜结果表明,虽然薄膜整体呈现外延结构,但其中...     

非晶态RE—TM(RE=Nd,Pr,TM=Fe,Co,Ni)薄膜的磁性和Pr的变价行为

本文通过对非晶态轻稀土Pr,Nd和过渡族金属Fe,Co,Ni薄膜合金的低温磁性研究,分别得到了(Pr,Nd)_x-(Fe,Co,Ni)_1-x合金中Pr,Nd和Fe,Co,Ni金属磁矩随成份x的变化,并且通过对磁矩的研究得到Pr离子的4f电子可能有退局域化的结论。 关键词：     

Tailoring the structural and magnetic properties of sol-gel derived Sm-Co nanogranular films

In this study, we investigated the microstructure, phase evolution and magnetic properties of nanogranular films of Sm-Co compounds processed by the sol-gel method. By controlling the compositional ratio of Sm:Co precursor concentration, nanogranular films consisting of three distinct hard magnetic phases namely, Sm₂Co₇, SmCo₅ and Sm₂Co₁₇ with coercivity values of 1.78, 2.94 and 2.12 kOe, respectively, were obtained through this technique.     

Improvement of magnetic properties and read/write characteristics in SmCo5 perpendicular thin films

An SmCo₅ alloy is a promising candidate for ultra-high density magnetic recording media because of its strong uniaxial magnetocrystalline anisotropy, whose constant, K_u, is more than 1.1×10⁸ erg/cm³. Recently, we successfully obtained high perpendicular magnetic anisotropy for a sputter-deposited SmCo₅ thin film by introducing a Cu/Ti dual underlayer. However, it is necessary to improve magnetic properties and read/write (R/W) characteristics for applying SmCo₅ thin films to perpendicular magnetic recording media. In this study, we focused on reduction of magnetic domain size and change of a magnetization reversal process of SmCo₅ perpendicular magnetic thin films by introducing carbon (C) atoms into the constituent Cu underlayer. The magnetic domain size became small and the ratio of coercivity (H_c) against magnetic anisotropy (H_k) which is an index of the magnetization reversal process was increased by adding C atoms. We also evaluated the R/W characteristics of SmCo₅ double-layered media including C atoms. The medium noise was decreased and signal-to-noise ratio increased by introducing the C. The addition of C into the Cu underlayer is effective for changing the magnetization reversal process, reducing medium noise and increasing SNR.     

非晶态Fe90-xBxZr10合金的磁性、电性和晶化

本文研究了部分B元素替代Fe对非晶态FeZr基合金磁性、电性和晶化的影响,并与非晶态FeB合金作了比较。解释了样品中每个FeZr原子的平均磁矩μ_FeZr和居里温度T_c随B含量x的增加而增加的原因,讨论了在不同的温区样品中可能存在的散射机制对电阻率的贡献以及影响晶化温度的因素。 关键词：     

Magneto-optical Faraday and Kerr effect of orthoferrite thin films at high temperatures

Orthoferrites present, as bulk materials, reorientation transitions of their magnetic moment alignment at temperatures depending on the rare-earth (RE) ion. In particular, orthoferrites (REFeO₃) with RE = Sm, Dy, present this transition at T _SRT = 443 K and 36 K, respectively. The spectra of the complex Kerr and Faraday angle have been measured on orthoferrite thin films (RE = Sm, Dy, Y), which were prepared by pulsed laser deposition on amorphous quartz substrates. The obtained spectra exhibit contributions of both surfaces and interfaces. Propagation effects of the polarized light in the magneto-optical medium which is interpreted in terms of a simplified theoretical formalism, is also observed. For selected photon energies, temperature dependent Faraday rotation measurements, , on orthoferrite thin films (RE = Sm, Dy, Y) have been performed. A quite different thermal variation compared to the bulk magnetization has been observed. Curie temperatures are found to be close to the bulk values or slightly larger by 10 K to 20 K as in the case of DyFeO₃ and YFeO₃. For RE = Sm and Dy, increases with increasing temperature contrary to the saturation magnetization, passes through a maximum at about 460 K and vanishes with a T _C of 647±18 K, 695 K for RE = Sm and Dy respectively. Received 28 July 2000     

衬底温度和硼掺杂对p型氢化微晶硅薄膜结构和电学特性的影响

以B₂H₆为掺杂剂,采用射频等离子体增强化学气相沉积技术在玻璃衬底上制备p型氢化微晶硅薄膜.研究了衬底温度和硼烷掺杂比对薄膜的微结构和暗电导率的影响.结果表明：在较高的衬底温度下很低的硼烷掺杂比即可导致薄膜非晶化;在实验范围内,随着衬底温度升高薄膜的晶化率单调下降,暗电导率先缓慢增加然后迅速下降,变化趋势与硼烷掺杂比的影响极为相似.最后着重讨论了p型氢化微晶硅薄膜的生长机理. 关键词： p型氢化微晶硅薄膜 衬底温度 晶化率 电导率     

Properties of a rare earth free L10-FeNi hard magnet developed through annealing of FeNiPC amorphous ribbons

The rare-earth-free hard magnetic L1₀-FeNi phase found in cosmic meteorites demonstrates potential as a next-generation permanent magnet. However, it is very difficult to artificially produce the L1₀-FeNi phase due to the low atomic diffusion coefficients of Fe and Ni near the order-disorder transition temperature (∼320 °C). Therefore, FeNiPC amorphous alloy systems exhibiting crystallization temperature (T_x) near the transition temperature were investigated. The amorphous alloys were annealed at T_x, resulting in high atomic diffusion. The structural and microstructural characterizations of annealed ribbons revealed the formation of L1₀-FeNi phase through observation of the superlattice peak. The magnetic property, such as coercivity (H_c), also indicated the formation of L1₀-FeNi phase, because the maximum H_c value is 641 Oe after the annealing process.     

Low temperature conversion electron Mössbauer spectroscopy on FexGe1−x amorphous thin films

Conversion Electron Mössbauer Spectroscopy has been performed between room temperature and 4.2 K on a series of thin films 1000 Å thick of amorphous Fe_xGe_1?x alloys, 0.4 ? x ? 0.60. It shows that the onset of ferromagnetism for x > 0.4 is associated with the apparition of a small magnetic moment in Fe atoms, increasing rapidly with x. For a given composition, the distribution in the values of moments born by the Fe atoms is large, reflecting the statistical fluctuations of the nearest neighbour environment of the iron atoms.