研究简报(Nd_(1-x)Er_x)_3 Fe_(27.31)Ti_(1.69)化合物的磁晶各向异性

用振动样品磁强计并结合X射线衍射准确判定了Nd2.4Er0.6Fe27.31Ti1.69化合物的磁晶各向异性方式,研究结果发现,Nd2.4Er0.6Fe27.31Ti1.69化合物的磁晶各向异性从室温时的易面转变到低温时的易锥.     

尺寸和空间分布对电沉积Co纳米线矫顽力的影响

研究了室温下不同直径的Co纳米线在不同取向下的磁化行为.实验结果表明:不同直径Co纳米线的矫顽力随着纳米线与外加磁场之间角度θ的增大而减小.理论上,应用蒙特卡罗模拟研究了纳米线矫顽力对角度θ的依赖关系.对比理论和实验的结果,得到如下结论:磁晶各向异性对Co纳米线磁特性起着重大的影响,Co纳米线的磁化反转过程不能简单地用球链模型中经典的一致转动模型来解释.     

双折射现象解析--在晶体中不可能发生多折射

从电磁理论出发解释了光在某些晶体中传播时呈现的双折射现象，通过本征值问题的解只有两个说明不可能发生三折射，四折射等多折射现象。     

侧向氟取代负介电各向异性液晶

负介电向异性（△ε）液晶广泛应用于DS、ECB、GH、FLC、PDLC、VA－TFTMDVA－TFT等模式的液晶显示中。此类液晶可以用来调节液晶混合物的△ε／ε⊥以改善液晶显示器件的电光特性，对侧向氟取代负介电各向异性液晶的结构、性质和应用作了论述。     

Effect of microstructure on the coercivity of HDDR Nd-Fe-B permanent magnetic alloy

The effect of the grain boundary microstructure on the anisotropy and coercivity was investigated in an HDDR Nd-Fe-B permanent magnetic alloy. Considering the special microstructure of its magnetic powder grain, an anisotropic theoretical model influenced simultaneously by the structure defect at the grain boundary and the exchange coupling interaction was put forward. The variations of the structure defect factors based on the nucleation and pinning mechanism with 2r ₀/lex (where r ₀ and lex are the defect thickness and the length of exchange coupling, respectively) were calculated. The results show that the coercivity mechanism of an HDDR Nd-Fe-B permanent magnetic alloy is greatly related to its microstructure defect at the grain boundary. For a fixed lex, when 2r ₀/lex < 1.67, the coercivity is controlled by the pinning mechanism; when 2r ₀/lex > 1.67, it is determined by the nucleation mechanism. The coercivity reaches the maximum when 2r ₀/lex = 1.67. The calculation result is consistent well with the experimental result given by Morimoto et al. Supported by the National Natural Science Foundation of China (Grant No. 50671055)     

用电镜对CoCr垂直磁化薄膜观察磁畴随温度的变化及居里点检测(英文)

本文研究了CoCr垂直磁化薄膜的磁畴随温度的变化。垂直磁化点畴变化为面内磁化羽状畴的转变温度在升温过程中为350℃。本实验测得CoCr膜的居里点T_c约在600℃附近。本文也分析了H_k或K_u随温度的变化要比M随温度的变化更快。这支持了垂直磁各向异性根源主要来自磁晶各向异性。显微照片也显示了自发磁化点畴的尺寸要比膜表面晶粒或膜断面晶柱的尺寸都要大,并都处在单畴状态。     

各向异性板的一种简化高阶理论

本文建立一种新的各向异性板的高阶理论,求出木理论的几个特殊问题的封闭解。与精确的弹性理论解比较,表明本文提出的理论对分析板的弯曲问题是十分有效的。     

HAMILTONIAN SYSTEM AND SIMPLETIC GEOMETRY IN MECHANICS OF COMPOSITE MATERIALS (Ⅱ)——PLANE STRESS PROBLEM

Fundamental theory presented in Part (I)^[8] is used to analyze anisotropic plane stress problems. First we construct the generalized variational principle to enter Hamiltonian system and get Hamiltonian differential operator matrix; then we solve eigen problem; finally, we present the process of obtaining analytical solutions and semi-analytical solutions for anisotropic plane stress problems on rectangular area.     

Triple quantum MQMAS spectroscopy of (I=7/2) in Na3Co(NO2)6 and trans-Co[(en2)(NO2)2]NO3 interplay between the quadrupole coupling and anisotropic shielding tensors

The purpose of this paper is to investigate the interplay between the chemical shielding anisotropy and quadrupole interaction in MQMAS spectra. in the compounds Na₃Co(NO₂)₆ and trans-Co[(en₂)(NO₂)₂]NO₃ provides model systems for such an investigation. Furthermore, only few results have been reported on the application of the MQMAS method to a spin I=7/2. The possibilities of the MQMAS spectroscopy for determining the relative orientation of the two tensors and its advantage over previous techniques are discussed. Reported experimental spectra at different spinning speeds of Na₃Co(NO₂)₆ are accurately reproduced by our theoretical simulations. The calculations are based on a recent approach, summarized in the present paper, which allows one to perform efficient simulations of MQMAS spectra including all interactions and their time-dependence throughout the experiment. This is necessary for calculating accurate MQMAS spectra including the spinning sideband pattern. In the case of trans-Co[(en₂)(NO₂)₂]NO₃ where the quadrupolar interaction and chemical shielding are stronger and their axes are non-coincident, the MQMAS spectrum is strongly distorted due to the unsufficient spinning speed and RF power. In this case, MAS at different spinning speeds is shown to provide valuable information.