Dy(Fe_(1-x)Ga_x)_2中畴壁的内禀钉扎和宏观量子隧道效应  

MACROSCOPIC QUANTUM TUNNELING OF THE MAGNETIZATION AND INTRINSIC PINNING OF DOMAIN WALLS IN Dy(Fe_(1-x)Ga_x)_2 COMPOUNDS

作　　者：钟文定[1] 刘尊孝[1] 陈海英[1] 李国忠[1] 

机构地区：[1]北京大学物理系,北京100871

出　　处：《物理学报》1995年第9期1516-1528,共13页Acta Physica Sinica

基　　金：国家自然科学基金;高等学校博士学科点专项科研基金

摘　　要：研究了赝二元立方化合物Dy(Fe_1-xGa_x)_2(x≤0.3)的磁性.观测到Ga对Fe的无序置换,导致磁性的重大改变.T>4K的磁性属于正常型,用畴壁内禀钉扎受到热激活的概念,解释了实验结果;由此导出的矫顽力随温度变化的公式(8)与实验符合得相当好.T<4K的磁性属于异常型,表现为退磁曲线有台阶和大跳跃、矫顽力随温度变化出现峰值、磁粘滞性系数与温度无关等.用畴壁隧道效应量子形核的概念,说明了实验结果,而且从理论上估算出由经典热激活到量子隧道效应的交界温度,得到的数值2.21—3.03K与实验值～3K相符.In this paper, we present a comprehensive study of the magnetic properties of pseudobinary cubic compounds Dy(Fe1-xGax)2 (x≤0.30). That the partial random substitution of Fe by Ga modifies significantly the magnetic properties at low temperatures are observed. At T > 4K, the intrinsic pinning model predicts the coercive fields (due to the thermal activation effects) will follow the equation (8) and in good agreement with the experimental results. At T < 4K, the anomalous behaviours such as the staircase and a large jumps of demagnetzation curve, the temperature dependence of coercivity exhibit an obvious peak and the magnetic viscosity is independent of temperature etc. were observed. The observed features are in accordance with theoretical suggestions on quantum nucleation of domain walls. For the compounds Dy(Fe1-xGax)2 (x ≤0.30), the experimental results suggest a crossover temperature Tq from the thermal activation to quantum tunneling regimes of-3 K, in reasonably good agreement with the values of 2.21-3.03 K calculated from theory.

关 键 词：MQTM 磁性 二元立方化合物 内禀钉扎 

分 类 号：O482.5[理学—固体物理]