Transition metal nitrides and their mixed crystals for spintronics.

Abstract

Anti-perovskite transition metal nitrides exhibit a variety of magnetic properties-such as ferromagnetic, ferrimagnetic, and paramagnetic-depending on the 3d transition metal. Fe4N and Co4N are ferromagnetic at room temperature, and the minority spins play a dominant role in the electrical transport properties. However, Mn4N is ferrimagnetic at room temperature and exhibits a perpendicular magnetic anisotropy caused by tensile strain. Around the magnetic compensation in Mn4N induced by impurity doping, researchers have demonstrated ultrafast current-induced domain wall motion reaching 3,000 m s-1at room temperature, making switching energies lower and switching speed higher compared with Mn4N. In this review article, we start with individual magnetic nitrides-such as Fe4N, Co4N, Ni4N, and Mn4N; describe the nitrides features; and then discuss compounds such as Fe4-xAxN (A = Co, Ni, and Mn) and Mn4-xBxN (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.