Au-Ni弱铁磁合金的自发磁矩和居里点

x=0.42—0.55的Au_1-xNi_x晶态合金是从液态直接淬火到室温,测量低温下这些合金的磁化曲线(2—70kOe),得到在温度1.5K下的自发磁矩值,并用Arrott-Noakes图线方法确定居里点。首先用Perrier等人提出的最近邻模型计算平均磁矩,和实验结果进行了比较。并提出最及次近邻模型,即考虑到次近邻的影响,假设一个Ni原子的最、次近邻18个原子有11个以上是Ni原子,它就具有和纯Ni一样的磁矩(0.606μ_B),否则磁矩为零,由此模型计算的平均磁矩值和实验结果比较符合。本文还对合金中自旋集团(spincluster)的存在和自旅集团之间的相互作用作了讨论,给出了表示自旋集团之间铁磁相互作用的平均内场μ_BH/k_B的值。关键词：

SPONTANEOUS MAGNETIC MOMENTS AND CURIE TEMPERATURES OF Au-Ni WEEKLY FERROMAGNETIC ALLOYS

The low-temperature magnetizations of liquid-quenched Au-Ni alloys containing 42 to 55 at% Ni have been measured in an uniform magnetic field (2 to 70kOe) using a motor-driven vibrating sample magnetometer. The spontaneous magnetic moments at 1.5 K were obtained. And the Curie temperatures were determined from Arrott-Noa-kes plots. The measured magnetic moments are first compared with the average moments calculated from Perrier nearestneighbor model. Furthermore, we not only consider the Ni nearest neighbors but also the Ni second-nearest neighbors. The simple model of an environment-dependent moment is presented. It is assumed that one Ni atom has a moment μ_Ni=0.606 μ_s if surrounded by at least 11 Ni atoms as nearest and second-nearest neighbors (the numbers of the nearest and the second-nearest neighbor are 18 for fee structure), and no moment if not. The calculated values from this model fit the measured values well. The existence of spin clusters and their interactions are discussed. The averagevalues of the internal field μ_BH/k_B, which present the ferromagnetic interaction betweenspin clusters, are estimated.