铁磁性微磁学理论的一个改进

本文用有效场方法,将Brown针对单晶均匀铁磁体的等温过程而建立的微磁学进行了改进,使它既可以考虑铁磁体结构和磁性的非均匀性的影响,又可以用来研究温度变化的过程。此外,对磁化强度矢量的平衡方程和运动方程的边界条件,做了较细致的讨论。     

TUNNEL MAGNETORESISTANCE IN THE FERROMAGNETIC TUNNEL JUNCTION WITH FERROMAGNETIC LAYERS OF FINITE THICKNESS SUBJECTED TO AN ELECTRIC FIELD

Based on the two-band model, we investigate the tunnel magnetoresistance(TMR) in ferromagnet/insulator (semiconductor)/ferromagnet(FM/I(S)/FM) tunnel junction covered on both sides by nonmagnetic metal layers subjected to an electric field. Our results show that TMR oscillates with the thickness of ferromagnetic layers owing to the quantum-size effect and can reach very large value under suitable conditions, which may in general not be reached in FM/I(S)/FM with infinitely thick ferromagnetic layer. Although the electric field causes the change of the oscillation period, phase and amplitude of the TMR, a large TMR is still obtained in some situations with the electric field. Furthermore, the electric field does not change the feature that TMR varies monotonously with the change of magnetization angle of the middle ferromagnetic layer.     

GIANT MAGNETORESISTANCE OF MAGNETIC SUPERLATTICES: QUANTUM SIZE EFFECT

In this paper the quantum size effect in giant magnetoresistance of magnetic superlattices is studied. The electrons are considered to be confined in a set of quantum wells, which are different for the ferromagnetic and antiferromagnetic ordering in magnetic superlattices. The oscillation of giant magnetoresistance with increasing thickness of the nonmagnetic spacer layer is explained. It is shown that the influence of quantum size effects on the giant magnetoresistance of magnetic superlattices is considerable.     

我国磁学和磁性材料研究的若干新进展

中国对古代磁学的发展曾作出过杰出的贡献．经过千余年的沉默，在我国磁学先驱者的努力下，我国磁学事业又得到极大发展．本文仅从物理角度回顾近年来我国磁学研究的部分成果：在稳态和业稳态铁基稀土永磁合金研究中具有国际先进水平的工作；对大克尔偏转角磁光膜探索中获得的突破性成果；对纯有机铁磁体这一对磁学基本问题提出挑战的课题方面所作出的重要结果；在布洛赫线物理这个新发展领域中具有重要意义的成果等．     

MOLIEN TYPE FUNCTION FOR ANTISYMMETRIZED POWER REPRESENTATION OF A FINITE GROUP

For antisymmetrized nth power of representation of a finite group G we define the Molien type generating function M (-) (G; z) where c is the multiplicity of the identity representation in the antisymmetrized nth power of representation of finite group G. We obtain a formula for M(-) (G; z) and two algorithms for its calculations using the characters only.     

自旋波之间的散射对铁磁共振曲线的影响

本文讨论了k≠0自旋波间的散射对共振吸收曲线的影响,得到了吸收曲线的ι级矩的严格的表达式。用微扰法求出了在一级近似下对吸收曲线的改正。     

希土金属中的s-f相互作用

本文利用量子力学中角动量理论的代数方法,对希土金属的s-f相互作用模型作了比较仔细的讨论,导出了s-f电子间相互作用的哈密顿量的一般形式。用算符形式的微扰论方法,求得了通过s-f相互作用而导致的f电子间f-f间接作用的有效哈密顿量的一般表达式。在保留到二极小项的情况下,除各向同性的交换作用以外,还得到了赝偶极矩作用。在所得结果的基础上,初步讨论了希土金属铁磁相的磁晶各向异性。指出了以上的结果可能解释的一些实验事实。     

非均匀铁磁体自发磁化的平均场理论

从描写非均匀铁磁体的平均场近似的非线性微分方程出发,本文用分支点理论处理相变现象。指出:(1)系统的居里点由线性化方程的最大本征值决定;(2)略低于居里点时系统磁化的空间分布可用相应的本征函数描写;(3)磁化的温度关系由参数a(T)～(1-T/T_C)^1/2表示。本文最后用薄膜和一个简单的模型为例指出方法的利用。 关键词：     

A DETERMINANT FOR THE TRANSFER MATRIX OF THE ONE-DIMENSIONAL DIRECTED BOND PERCOLATION WITH FURTHER NEIGHBOUR BONDS

The rigorous proof of the relation det is given. This relation has been used to obtain the exact critical surface and the correlation length exponents of the one-dimensional directed bond percolation problem with bonds connecting 1～Lth nearest neighbours. A~((L)) is related to the transfer-matrix by (7). q_i is related to the occupation probability of the i-th nearest neighbour bond p_i by q_i=1-p_i (i=1, 2, ..., L). f_L is a multi-varlable polynomial in q_4's.     

Brown方程的分歧解

本文推广和应用分歧理论的微扰法,在对称情况下,求解了Brown方程的最大分歧点{0,H_n}和从此点发出并在此点附近的分歧解。这直接关系着反磁化形核问题的解决。结论指出:分歧解具有±D₂(H_n-Hu₀)^1/2的形式。常数H_n和D₂由铁磁体的磁性和几何决定,而空间函数u₀仅与几何有关。文中并求出了它们的表达式。