Heusler合金是一种具有诸多优异性能的合金，在形状记忆、磁制冷方面均有着广泛的应用前景。通过考虑Heusler合金中的原子占位、价电子数、原子无序程度和交换作用强度，我们可以灵活地根据一些简单的规律设计新材料。

磁矩补偿型材料最近受到人们的关注，在其中发现了极大的交换偏置效应，而交换偏置在磁存储、自旋阀、磁性隧道结和永磁等材料中都有广泛应用。本课题旨在利用第一性原理计算结合实验的方法，以Mn3Z合金为基础寻找新的磁补偿型Heusler合金，并进一步结合实验探究其可能存在的大交换偏置性能。我们通过计算预测了以Mn3Ge为基础的新型磁补偿体系，并通过一系列的实验制备和结构、磁性表征，对Mn3Ge中的交换偏置效应进行了初步研究。具体结果如下：47860

（1）以Mn2+xY1-xZ 为基础寻找完全磁补偿的成分，通过计算首先预测了在Y=Ni、Pd、Pt，Z=Ge时可以获得目标成分，随后通过进一步计算得出，Mn2+xNi1-xGe、Mn2+xPd1-xGe和Mn2+xPt1-xGe 在x=0.190、0.187、0.212时分别可以得到完全磁补偿状态。该状态即为我们目标的可能拥有大的交换偏置效应的体系。

（2）通过电弧熔炼和特定的热处理方法得到了单相的四方D022型Mn3.4Ge合金样品，ZFC-FC曲线表明该合金中存在有交换偏置效应。

毕业论文关键词：Heusler合金 磁补偿型 交换偏置 第一性原理

毕业设计说明书外文摘要

Title  Research on magnetic compensated Heusler alloys    

Abstract

Heusler alloy is a kind of compound which has many good properties and a wide range of applications such as shape memory effect, magnetocaloric effect. The story of their success is based on the fact that new materials can be designed in the flexible structure of the Heusler family on the basis of simple rules taking into account the position of the atoms, the number of valence electrons, the degree of atomic disorder and the strength of the exchange interactions.

Recently, the magnetic compensated materials have attracted many concern on account of the giant exchange bias effect in them, which has potential applications in magnetic storage, spin valve, magnetic tunnel junctions and permanent magnet applications. In this article, we aimed to design new kinds of magnetic compensated Heusler alloys based on the system of Mn3Z alloys by first-principle calculations together with experimental research, and concentrate on the possible EB effect in it.Here, we have successfully predicted the new magnetic compensated state in Mn3Ge system, and after sample preparation and their structural and magnetic properties measurement, we have carried out primary research on the EB effect in Mn3Ge alloys, the conclusion are shown here： 

(1) To search for the composition of fully compensated magnetic state based on the formula of Mn2+xY1-xZ, first we predicted that we can obtain the target content when Y=Ni、Pd、Pt,Z=Ge, and subsequently when x=0.190、0.187、0.212, Mn2+xNi1-xGe、Mn2+xPd1-xGe and Mn2+xPt1-xGe can be fully compensated respectively, which is the system predicted to have giant EB effect. 

(2) The ingots were prepared by using a vacuum arc melting and afterwards undergoing a specific heat treatment, to obtain the tetragonal samples. The research on the ZFC-FC curves of the alloys shows that there exists exchange bias effect. 

Keywords：Heusler alloys, compensated, exchange bias, first-principle calculations 

     目 次

1  绪论 1

1.1  前言 1

1.2  Heusler合金概况 1

1.2.1  Heusler合金晶体结构 1

1.2.2  Heusler合金中的四方畸变