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Theoretical investigations of Anomalous Magnetism in Amorphous Transition Metals and Alloys.

非晶态过渡金属和合金中反常磁性的理论研究。

基本信息

批准号：
02640283
负责人：
KAKEHASHI Y.
金额：
$ 0.58万
依托单位：
Hokkaido Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

Recently, anomalous magnetic behaviors such as the spin glass (SG) state and high Curie temperatures (>1800 K) have been found in Fe-rich and Co-rich amorphous transition metal alloys. In order to clarify the anomalous behaviors, we have investigated the magnetism of amorphous transition metals on the basis of the finite temperature theory of local environment effect in amorphous metallic magnetism. Our conclusions are summarized as follows.1. The simple ferromagnetism in Fe, Co, and Ni is drastically changed by the structural disorder ; (1) Amorphous Fe shows the itinerant electron SG because of the nonlinear magnetic couplings between Fe local moments and the local environment effects on the amplitudes of local moments. (2) The Curie temperature in amorphous Co is enhanced by about 400 K because of the magnetic energy gain due to the shift of the non-interacting density of states. (3) The strong ferromagnetism in amorphous Ni is weakened because of the same reason.2. We examined the SG around amorphous Fe, so that we found the following new results. (1) There exists the cluster SG region with the ferromagnetic clusters between the SG and the ferromagnetism when the d electron number is varied. (2) Re-entrant SG was found near the ferromagnetic boundary. Theoretical results semi-quantitatively explained the magnetic-field and pressure effects on the re-entrant SG in Fe-rich Fe-Zr and Fe-La amorphous alloys. (3) The strong anomaly of the forced volume magnetostriction at the re-entrant SG temperature is characteristic of the itinerant SG which is never seen in the insulator systems.

近年来，在富Fe和富Co的非晶态过渡金属合金中发现了自旋玻璃态和高居里温度（>1800 K）等反常磁性行为。为了阐明这些反常行为，我们在非晶态金属磁性局域环境效应的有限温度理论基础上研究了非晶态过渡金属的磁性。我们的结论总结如下。1.结构无序使Fe、Co和Ni的简单铁磁性发生了显著变化：（1）非晶Fe表现出巡游电子SG，这是由于Fe局域磁矩之间的非线性磁耦合以及局域环境对局域磁矩幅值的影响。(2)非晶Co的居里温度提高了约400 K，这是由于非相互作用态密度的移动引起的磁能增益。(3)非晶态Ni的强铁磁性也因同样的原因而减弱.我们检查了非晶Fe周围的SG，因此我们发现了以下新结果。(1)当d电子数变化时，在SG和铁磁性之间存在铁磁团簇聚集的SG区域。(2)在铁磁边界附近发现了重入SG。理论结果半定量地解释了磁场和压力对富铁Fe-Zr和Fe-La非晶合金中重入SG的影响。(3)在重入SG温度下的强迫体积磁致伸缩的强烈异常是巡游SG的特征，这在绝缘子系统中是从未见过的。