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

近年来，在富Fe和富Co的非晶态过渡金属合金中发现了诸如自旋玻璃态(SG)和高居里温度(&GT；1800K)等反常磁性行为。为了阐明这种反常行为，我们在非晶态金属磁性局域环境效应的有限温度理论的基础上，研究了非晶态过渡金属的磁性。我们的结论总结如下：1.结构无序改变了Fe、Co、Ni的简单铁磁性：(1)由于Fe局域磁矩和局域环境对局域磁矩幅值的非线性磁耦合作用，非晶态Fe表现为巡游电子SG。(2)非晶态Co中的居里温度由于非相互作用态密度的移动而产生的磁能增益使居里温度提高了约400K。(3)由于同样的原因，非晶态Ni的强铁磁性被削弱了。我们研究了无定形Fe周围的SG，得到了以下新的结果。(1)当d电子数变化时，在SG和铁磁性之间存在具有铁磁团簇的团簇SG区。(2)在铁磁边界附近发现了重入的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非晶态合金中再入相的影响。(3)在再入温度下，强迫体积磁致伸缩的强烈反常是巡回SG的特征，这在绝缘体系统中是不存在的。

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.