混合Heisenberg自旋体系动态相变的滞后标度

采用Monte Carlo方法对离散混合经典Heisenberg自旋体系在周期性外场驱动下动态相变行为进行了模拟计算.在典型Heisenberg自旋体系的哈密顿量基础上,引入表征非晶相的随机各向异性能项(比例为X)和表征晶体相的单轴各向异性能项(比例为1-X),考察了该混合自旋体系磁滞后回线面积A_area随X和单轴各向异性常数A及随机各向异性常数D的变化规律,并确定了该类自旋体系动态相变新的滞后标度关系A_area-A^δD^{η关键词： 海森堡模型 Monte Carlo模拟 磁滞标度 非晶纳米晶}

SCALING HYSTERESIS OF DYNAMICAL TRANSITION OF DILUTED HEISENBERG SPIN SYSTEM

The Monte Carlo method was employed to perform the numerical simulation for clas sical discrete diluted Heisenberg spin system driven by an oscillating external magnetic field. To form the diluted spin system based on isotropic Heisenberg mo del, we introduced in the Hamiltonian of a typical Heisenberg model both random anisotropy energy term characterizing amorphous state with a proportion X an d uniaxial anisotropy energy term representing crystalline state with a proporti on 1-X. The dynamical transition behavior of the Spin system mentioned abov e, hysteresis loop scaled with parameter X and random as well as uniaxial an isotropy constant D and A, respectively, was studied in detail. It has b een put forward a scaling relationship between hysteresis loop area and paramete r X, A and D as below:Aarea-AδDηXσ. T he main conclusions can be summarized below:(1)At a specific value X(defined as Xmin), the investigated system gains minimal hysteresis which has been proved experimentally in our another investigation. (2) The exponents δ, η and σ of the diluted spin system are universal constants, and the sum of δ+η(～0.9) equals the exponent δ,η of single either uniaxial or rand om anisotropy spin system. (3)The specific value Xmin versus logarithm of the ratio of A/D shows a peculiar sigmoidal trend.