共查询到20条相似文献,搜索用时 140 毫秒
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用中子相干非弹性散射测量了Fe_3Si在14K的自旋波色散关系。从自旋波二次方色散关系得到低温下自旋波劲度系数D_0=270meV·A~2。用Heisenberg模型可进一步导出Fe_3Si的有效交换积分J_(eff)。从磁化强度的温度依赖关系也获得了一个自旋波劲度系数D_m(O)。从两种不同方法获得的劲度系数的比较中发现在Fe_3Si中可能存在着Stoner激发,与早先工作相联系,本文还给出了从14K直到居里温度自旋波劲度系数D的温度依赖关系。 相似文献
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用单辊急冷法制备了非晶态(Fe1-xVx)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2.08μB和-5.08μB。居里温度Tc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: 相似文献
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本文给出一张既能考虑A-15结构型变,又能描述A-15型化合物Tc(超导临界温度)变化规律的图。从而预言:所述A-15系列中大概不会存在Tc很高(>25K)的化合物;铌系列中Nb3Ge的Tc可能是最高的;钒系列中Tc可望还能提高(>17.1K),V3Ge可望提高到12K以上。检查Nb3Si,得不到Geller那样的乐观估计,并认为:以新工艺得到的A-15相Nb3Si,是以牺牲正当化学配比或改变正常原子体积为代价而获得的非理想结构。从Tc与半径比关系及理想A-15结构对半径比的要求来看,笔者认为文献上关于Nb3Si在有较高Tc(>23K)的种种预言,都是缺乏充分依据而不足置信的。
关键词: 相似文献
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本文叙述了利用电子显微镜对含10%Si和5%Al的Fe-Si-Al高导磁合金薄膜进行的结构研究。发现了基体为有序面心立方Fe3(Al,Si)结构,其晶格参数为5.70±0.03?,该值在Fe3Si和Fe3Al晶格参数之间,说明部分Si原子为Al原子所置换。并获得三套基体和析出相合成的电子衍射图,相应确定了基体和析出相的取向关系:(001)基‖(110)相;[100]基‖[00I]相;[010]基‖[I10]相。对析出相的萃取碳复型,在电子显微镜中进行选区衍射,获得了立方Fe3(Al,Si)Cx相的结构。提出:Fe原子占据面心;Al或Si原子占据顶角;C原子占据体心的看法。
关键词: 相似文献
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用布里渊散射技术测量了BCVIG(Bi3-2xCa2xFe5-xVxO12)单晶的磁振子散射谱,同Sande-rcock,Wettling对YIG以及刘玉龙等人对Bi-YIG单晶的测量相比,我们得到了除主峰之外的连续谱带。按照偶极-交换自旋波理论讨论了测到的自旋波谱。测量还表明BCVIG单晶的自旋波劲度系数D比YIG和Bi-YIG单晶大得多,讨论了D增大的原因,研究了D与入射激光功率的关系。
关键词: 相似文献
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研究了低温下NdMnO3单晶的比热随温度和磁场的变化(2K≤T≤200K,0T≤H≤8T ).对应于 Mn磁矩亚晶格的A型反铁磁(A-AF)相变,零场下的比热曲线在85K附近出现尖锐的λ形峰,随 着磁场的增加,此λ峰降低展宽而且平滑变化,这与此温度附近磁化强度的变化规律一致. 与磁有序相变相关的熵变约为理论值的26%,这可能是由于磁有序涨落延续在较大温区造成 的.在20K以下,比热曲线出现了明显的肩膀形状的Schottky反常,其峰值随着磁场的增加而 逐渐向高温移动.考虑了低温下比热的各种贡献,根据Nd3+位有效分子场(H mf) 引起的Nd3+基态双重态(GSD)劈裂对上述现象进行了解释.通过对2K≤T≤2 0K,0T≤ H≤8T范围内比热数据的拟合,得到了样品的GSD劈裂,德拜温度和A-AF自旋波劲度系数以及 它们对磁场的依赖关系.发现GdFeO3型八面体旋转引起的A-AF结构中Mn磁矩亚晶 格的铁磁成分可能是Hmf的来源.
关键词:
比热
Schottky反常
反铁磁相变 相似文献
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由弱磁场下光泵自旋交换、强磁场中核磁共振测量方法,获得激光极化低压同位素129Xe气体的核自旋弛豫率1/T1及其与N2气压力、环境温度的关系.结果表明:在291K的室温下,对于0~11 333.05Pa的N2气压力范围,1/T1随着N2气压力的增加而增大;N2气压力为1 466.63Pa时,1/T1随着样品温度从234K到292K增高而减小 相似文献
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WU Feng-Min XU You-Sheng LI Qiao-Wen 《理论物理通讯》2006,46(2):332-336
A comprehensive simulation model -- deposition, diffusion, rotation, reaction and aggregation model is presented to simulate the formation processes of ramified clusters on liquid surfaces, where clusters can disuse and rotate easily. The mobility (including diffusion and rotation) of clusters is related to its mass, which is given by Dm = Dos^-γD and θm = θos^-γθ, respectively. The influence of the reaction probability on the kinetics and structure formation is included in the simulation model. We concentrate on revealing dynamic scaling during ramified cluster formation. For this purpose, the time evolution of the cluster density and the weight-average cluster size as well as the cluster-size distribution scaling function at different time are determined for various conditions. The dependence of the cluster density on the deposition flux and time-dependence of fractal dimension are also investigated. The obtained results are helpful in understanding the formation of clusters or thin film growth on liquid surfaces. 相似文献
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A modified fractal growth model based on the deposition, diffusion, and aggregation (DDA) with cluster rotation
is presented to simulate two-dimensional fractal aggregation
on liquid surfaces. The mobility (including diffusion and rotation)
of clusters is related to its mass, which is given by Dm=D0
s-γD and θm=θ0s-γθ, respectively. We concentrate on revealing the details of the influence of deposition flux F, cluster diffusion factor
γD and cluster rotation factor γθ on the dynamics of fractal aggregation
on liquid surfaces. It is shown that the morphologies of
clusters and values of cluster density and fractal dimension
depend dramatically on the deposition flux and migration factors of clusters. 相似文献
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K. Yoshimura M. Takigawa Y. Takahashi H. Yasuoka M. Mekata Y. Nakamura 《Journal of magnetism and magnetic materials》1987,70(1-3):11-13
The nuclear spin-lattice relaxation rate, 1/T1, has been measured in weak itinerant ferromagnets Y(Co1−xAlx)2. The temperature and magnetic field dependence of 1/T1T has been found to be well described by the self-consistent renormalization (SCR) theory of spin fluctuations. The parameters characterizing spin fluctuations in this system were estimated from NMR and magnetic measurements. The temperature dependence of susceptibility calculated from these parameters well reproduces the experimental results. 相似文献
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A. Bousseksou A. Ducouret-Crze M. Guillot J. Hamman J. Linares J. Nasser F. Varret 《Journal of magnetism and magnetic materials》1992,110(3):295-298
Magnetic measurements on single crystals and Mössbauer spectra of powders under magnetic field, recorded on Fe2+ doped K2ZnF4, have been analyzed in the spin Hamiltonian formalism. The data slightly depart from the expectations of a spin 2 in D4h symmetry. The occurrence of vibronic effects is discussed. 相似文献
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D. A. Coombe 《Physica A》1980,100(3):472-495
As an application of the general theory given in the previous paper1), distorted wave Born approximation calculations on the depolarized linewidths for H2 and D2 systems are presented. An assumed square well model for the spherical potential and dominant P2 and quadrupole-quadrupole nonspherical interactions are used to analyze the temperature dependence of both DPR and rotational Raman linewidths. Comparison with the excellent experimental results of van den Hout and coworkers2,3 is made and satisfactory agreement is found. 相似文献
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The energy spectra of three-axial ferromagnets like U3P4 and ferrimagnets like U3Sb4 are presented and their properties are discussed. In case of U3Sb4 we find an interesting example of a magnetic structure which, due to the single-ion anisotropy, is unstable in the spin wave approximation. The k2 dependence of magnon energies requires re-examination of the temperature dependence of the magnetisation and of the specific heat. 相似文献
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A. I. Tovstolytkin N. A. Belous I. V. Lezhnenko 《Journal of magnetism and magnetic materials》1994,130(1-3):293-296
We present here the detailed analysis of the magnetic behavior of the Co0.53Ga0.47 alloy, especially at temperatures above the freezing temperature Tf = 10 K. Low field static magnetization measurements were performed by using the SQUID magnetometer in the temperature range 5–65 K and magnetic fields up to 100 Oe. The temperature dependence of the field cooled susceptibility πFC(T) at T > Tf has an anomaly, which is displayed in the double change of the curvature near Ts = 24 K. The data of magnetization MFC in an external field H lie on a universal curve MFC(H/T) at temperatures Tf < T < Ts. The plots of π-1FC(T) and non-linear magnetic susceptibility πnlFC(T-3) are linear lines in the temperature range Tf−Ts. The strong deviation of π-1FC(T) and πnlFC(T-3) from straight line, taking place at T Ts, indicates that Ts is an upper temperature limit of the classical superparamagnetic behavior with the constant cluster moment. The results suggest that such phenomena may be fairly universal for spin glasses. 相似文献
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基于~(85)Rb原子5S1/2-5P3/2-5D_(5/2)阶梯型能级系统(780 nm+776 nm),利用高信噪比的电磁诱导透明谱对~(85)Rb原子5D_(5/2)态超精细分裂进行测量.其中,频率校准是通过位相型电光调制器和共焦法布里-珀罗腔共同实现的.通过测量~(85)Rb原子5D′5/2态(F′=5),(F′′=4)及(F′′=3)之间的超精细分裂,我们确定了~(85)Rb原子5D_(5/2)态的磁偶极超精细相互作用常数(A=-(2.222±0.019)MHz)和电四极超精细相互作用常数(B=(2.664±0.130)MHz). 相似文献
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The spin wave spectrum of chemically disordered Pd0.5Fe0.5 has been determined by neutron inelastic scattering. At small wavevectors, the dispersion curve is quadratic and isotropic with a spin wave stiffness constant of 47.9 ± 3.3 THz Å2, at room temperature. There is little sign of the anisotropic behaviour observed in the ordered alloy Pd3Fe. 相似文献