Magnetic moment and exchange interaction in Ni-Gd single and amorphous alloy by MCD and MCP

本项目的主要目的是在实验上重新考虑稀土（RE）-过渡金属（TM）体系中著名的“电荷转移模型”，即RE的外层电子转移到TM的3d带，TM的磁矩随着RE含量的增加而逐渐减小。作为电荷转移模型的代表之一，我们选择了GdNi_2Laves相，在该相中，由于RE的外层电子填充了Ni的3d带，Ni的磁矩变为零。此外，还从磁矩和交换作用J_2两个直接反映稀土-TM合金中磁电子行为的方面，研究了稀土-TM合金3d，4f，5d，6s中磁电子的<ij>行为，为直接确定Ni的3d带是否被填充，软X射线磁性圆二色性（MCD）是一种强有力的工具，MCD还提供了其它信息，如5 pm磁矩与角动量的比值 ...更多信息 样品的磁性结构和磁性贡献。此外，磁康普顿轮廓（MCP）可以提供一些有用的信息，关于磁矩的组成和磁结构。从宏观上看，通过对样品磁化强度随温度变化的分子场分析，给出了RE-TM系统中三个交换作用常数Jij，其中包括磁性电子的行为.软X射线MCD测量表明：（1）Ni的3d带在GdNi_2中没有被填充，在GdNi中也没有被填充.（2）在GdNi_2和GdNi中确实存在由3d电子引起的Ni磁矩，并且与Gd的磁矩反平行耦合，这是含Gd的TM重稀土的一般规律。（3）由轨道角动量贡献产生的磁矩比金属Ni的大，MCP清楚地表明Ni保留了GdNi_2的磁矩，并且与Gd的磁矩反平行耦合。此外，分子场分析成功地导出了三个交换相互作用常数，并解释了基于亚铁磁性的反磁化率的类Curie Weiss行为。少

The main aim of this project was to reconsider experimentally the famous and well-known "charge transfer model" in Rare Earth(RE)-Transition metal(TM) systems where the outer shell electrons of RE transfer to the 3d band of TM and the magnetic moment of TM decreases gradually with the increase of RE contents. As one of the representation of charge transfer model, we have selected the GdNi_2 Laves phase where the Ni magnetic moment becomes zero because of the filling of Ni 3d band from the outer shell electrons of RE. In addition, the behaviors of magnetic electrons in RE-TM systems such as 3d,4f,5d,6s were investigated in terms of the magnetic moment and exchange interactions J_<ij> which reflect directly the behaviors of magnetic electrons in RE-TM alloys.In order to confirm directly whether the 3d band of Ni is filled or not, the soft X-ray magnetic circular dichroism (MCD) is a powerful tool and the MCD gives other informations such as the ratio of 5pm magnetic moment to angular mom … More entum contribution and the magnetic structure of the sample. Furthermore the magnetic Compton profile (MCP) can give some useful informations regarding the magnetic moment of the consitituents and the magnetic structure. From the macroscopic point of view, the molecular field analysis of the temperature dependence of magnetization of the sample is useful to provide us three exchange interaction constants Jij which include the behaviors of the magnetic electrons in the RE-TM systems.The soft X-ray MCD measument reveals that(1)the 3d band of Ni is not filled in GdNi_2 and also in GdNi(2)the Ni magnetic moment stemming from 3d electrons does exist in GdNi_2 and GdNi and couples antiparallel to that of Gd which is the general rule for the TM-heavy RE including Gd.(3)the magnetic moment due to orbital angular momentum contribution is relatively larger than that of Ni metal.The MCP shows clearly that the Ni retains a magnetic moment in GdNi_2 and couples antiparallel to that of Gd. In addition, the molecular field analysis succseeds in deriving out three exchange interaction constants and explains the Curie Weiss-like behavior of inverse susceptibility based on the ferrimagnetism. Less