Manipulation of saturation magnetization and perpendicular magnetic anisotropy in epitaxial CoxMn4-xN films with ferrimagnetic compensation

摘要

Spintronics devices utilizing a magnetic domain-wall motion have attracted increasing attention, and ferrimagnetic materials with almost-compensated magnetic moments are highly required to realize the fast magnetic domain-wall motion. Here, we report a key function for this purpose in the antiperovskite CoxMn4-xN film. We have grown CoxMn4-xN films with various Co/Mn ratios on SrTiO3(001) by molecular-beam epitaxy. High-quality growth is confirmed and a perpendicular magnetization emerges at x = 0, 0.2, 0.5, and 0.8, whereas it turns into in plane for x >= 1.1. The saturation magnetization M-S decreases as x increases and reaches a minimum value of 15 emu/cm(3) at x = 0.8. Then, it increases with x when 0.8 <= x <= 3.6 and saturates. These results indicate that M-S and magnetic anisotropy of CoxMn4-xN films can be manipulated by the Co composition. X-ray absorption spectroscopy and magnetic circular dichroism measurements revealed that Co atoms tend to occupy the I site in the antiperovskite lattice and reasonably explains the origin of minimum M-S near x = 0.8, where a compensation of magnetic moments occurs among different atomic sites. We consider that the nearly compensated ferrimagnetic Co0.8Mn3.2N is suitable for application to current-induced domain-wall motion devices.