Mn2NiSn掺杂Ni、Co体系的结构与磁性研究

本文通过在Heusler合金Mn2NiSn中掺杂Ni、Co元素对其结构与磁性交换作用变化进行了研究。结果表明，在Mn2-xNi1+xSn体系中，随着Ni逐渐替代Mn，合金结构会由立方XA逐渐向L21结构转变。由于Ni原子相对于Mn原子具有较小的原子半径，Ni2MnSn相对于Mn2NiSn体积大概收缩1.2%。Mn含量的减少使得最近邻的Mn(A)-Mn(B)间反铁磁交换作用减弱，导致居里温度由x = 0时的519 K接近线性的降低到x=1时的340 K。当用Co元素替换部分Mn元素时，即Mn2-yCoyNiSn中，复杂的原子占位使得Mn(A)-Mn(B)交换作用降低的同时伴随着Co-Mn之间铁磁交换作用的增强，两者交换作用的竞争导致居里温度先降低后升高，临界点出现在y = 0.3处。在Mn2Ni1-zCozSn体系中，当Co替代部分Ni时，由于Ni-Mn之间的交换作用小于Co-Mn之间的交换作用，交换作用的增强导致居里温度随着Co含量的增加逐渐升高。室温下的饱和磁化强度也随着掺杂量的增大逐渐增大。

The structures and magnetisms of Ni/Co-doped Mn2NiSn

The influences of Co and Ni doping on the structure and magnetic interaction of Heusler alloy Mn2NiSn are studied in this paper. It is found that the structure of the alloy changes from cubic XA to L21 in Mn2-xNi1+xSn when x increases from 0 to 1. The volume of Ni2MnSn shrinks about 1.2% relative to Mn2NiSn because the radius of Ni atom is smaller than that of Mn atom. The replacement of Mn with Ni weakens the antiferromagnetic exchange between Mn(A)-Mn(B), resulting in the Curie temperature decreases from 519 K in Mn2NiSn to 340 K in Ni2MnSn. When partial of Mn is replaced by Co in Mn2-yCoyNiSn, the competition of the exchange interaction between Mn(A)-Mn(B) and between Co-Mn leads to the Curie temperature decreasing first and then increasing. When Co replaces Ni in Mn2Ni1-zCozSn, the Curie temperature increases with the increase of Co content due to exchange interaction between Ni-Mn is smaller than that between Co-Mn. At room temperature, the saturation magnetization increases with the increase of doping amount.