SrFeO2在高压下的结构演变
关键词 半金属材料 铁磁性 SrFeO2 自旋转换
毕业论文设计说明书外文摘要
Title the study on the property of SrFeO2 under high pressure
Abstract
The discovery of half metallic materials is receiving much more attention. Numerous studies suggested that structural evolution of half-metallic materials would take place under high pressure. In this paper, the author focuses mainly on the magnetic transformation of Fe of SrFeO2 which is an unprecedented material with quadruple metal irons complexes. Under normal atmospheric, this material is an excellent antiferromagnetic insulator when the temperature reaches to 473k. However, the spin configuration converts into intermediate spin state (s = 1) when the figure beef up to 34Gpa, this conversion process is accompanied with the resistivity decreased significantly, and the SrFeO2 is transformed into metal state. In addition, when the environment is maintained at its transition pressure, the anti-ferromagnetic state turns into ferromagnetic state. When SrFeO2 is in the magnetic energy, the energy power is lower than it is in the anti-ferromagnetic, indicating that the condition of ferromagnetic covers the majority proportion which is, hereafter, the actual situation..The conversion from metallicity to semi-metallicity is functioned by SrFeO2, and the spin conversion is converted from the metal to the magnetic conversion.
Keywords Semi metallic material Ferromagnetic SrFeO2 Spin conversion
1 绪论 1
1.1半金属材料及其性质 2
1.2铁磁性与反铁磁性 3
1.2.1铁磁性 4
1.2.2反铁磁性 5
1.3 半金属铁磁性的过渡金属氧化物 6
1.3.1 CrO2的半金属铁磁性 7
1.3.2 双钙钛矿Sr2FeMoO6的半金属铁磁性 7
1.4 本论文的工作 8
2 理论基础和计算软件 9
2.1 密度泛函理论 12
2.2 第一性原理下的密度泛函算 13
2.3 Monte Carlo模拟 14
2.4 VASP计算软件 15
2.5 计算方法16
3 高压对SrFeO2物性的影响18
3.1 高压下SrFeO2几何结构的变化19
3.2 高压对SrFeO2磁学特性的影响 19
3.3 高压对SrFeO2电学特性的影响 21
4 计算结果及分析 22
4.1什么是U以及它的作用22
4.2 不同U的对SrFeO2物性的影响23
结论 24
致谢 25
参考文献26
1 绪论
1.1 半金属材料及其特性
1983年，de Groot等人（荷兰Nijimegen大学）偶然发现了一种全新的能带结构，这种前所未有的能带结构出现在合金NiMnSb和PtMnSb中，半金属理论由此诞生[1]。这种新型能带包括两个自选方向相反的电子构成的子能带，既定电子自旋方向向上的能带将表现出金属性（亦即导带中存在费米面），电子自旋方向向下的能带将表现出半导体相应的性质或者绝缘体（亦即价带和导带之间存在费米面）。于是，具有这种前所未有的能带结构的物质在宏观上能表现金属性，在微观上又表现了金属性和绝缘性的矛盾共现，虽然这是由于这种半金属磁体在晶体结构等性质的因素而产生的。自此，半金属材料被定义为是具有以两种自旋方向相反的电子为特征的新型材料。半金属材料的发现也为自旋电子学的发展提供了动力。
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