First-principles calculations of magnetic properties for analysis of magnetization processes in rare-earth permanent magnets.

It has been empirically known that the coercivity of rare-earth permanent magnets depends on the size and shape of fine particles of the main phase in the system. Also, recent experimental observations have suggested that the atomic-scale structures around the grain-boundaries of the fine particles play a crucial role to determine their switching fields. In this article, we review a theoretical attempt to describe the finite temperature magnetic properties and to evaluate the reduction of the switching fields of fine particles of several rare-earth permanent magnetic materials based on an atomistic spin model that is constructed using first-principles calculations.

Perpendicular magnetic tunnel junction with a strained Mn-based nanolayer.

A magnetic tunnel junction with a perpendicular magnetic easy-axis (p-MTJ) is a key device for spintronic non-volatile magnetoresistive random access memory (MRAM). Co-Fe-B alloy-based p-MTJs are being developed, although they have a large magnetisation and medium perpendicular magnetic anisotropy (PMA), which make it difficult to apply them to a future dense MRAM. Here, we demonstrate a p-MTJ with an epitaxially strained MnGa nanolayer grown on a unique CoGa buffer material, which exhibits a large PMA of more than 5 Merg/cm(3) and magnetisation below 500 emu/cm(3); these properties are sufficient for application to advanced MRAM.

Local density of states around a magnetic impurity in high- T(c) superconductors based on the t-J model.

The local density of states (LDOS) around a magnetic impurity in high- T(c) superconductors is studied using the two-dimensional t-J model with a realistic band structure. The order parameters are determined in a self-consistent way within the Gutzwiller approximation and the Bogoliubov-de Gennes theory. In sharp contrast with the nonmagnetic impurity case, the LDOS near the magnetic impurity shows two resonance peaks reflecting the presence of spin-dependent resonance states.