Transition metal nitrides and their mixed crystals for spintronics
Keita Ito, Syuta Honda, Takashi Suemasu
Abstract
Abstract Anti-perovskite transition metal nitrides exhibit a variety of magnetic properties—such as ferromagnetic, ferrimagnetic, and paramagnetic—depending on the 3 d transition metal. Fe 4 N and Co 4 N are ferromagnetic at room temperature (RT), and the minority spins play a dominant role in the electrical transport properties. However, Mn 4 N is ferrimagnetic at RT and exhibits a perpendicular magnetic anisotropy caused by tensile strain. Around the magnetic compensation in Mn 4 N induced by impurity doping, researchers have demonstrated ultrafast current-induced domain wall motion reaching 3000 m s −1 at RT, making switching energies lower and switching speed higher compared with Mn 4 N. In this review article, we start with individual magnetic nitrides—such as Fe 4 N, Co 4 N, Ni 4 N, and Mn 4 N; describe the nitrides’ features; and then discuss compounds such as Fe 4− x A x N (A = Co, Ni, and Mn) and Mn 4− x B x N (B = Ni, Co, and Fe) to evaluate nitride properties from the standpoint of spintronics applications. We pay particular attention to preferential sites of A and B atoms in these compounds, based on x-ray absorption spectroscopy and x-ray magnetic circular dichroism.