Manipulation of saturation magnetization and perpendicular magnetic anisotropy in epitaxial Co_xMn_(4-x)N films with ferrimagnetic compensation

摘要

Spintronics devices utilizing a magnetic domain-wall motion have attracted increasing attention, and ferri-magnetic 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 Co_xMn_(4-x)N film. We have grown Co_xMn_(4-x)N films with various Co/Mn ratios on SrTiO_3(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 Co_xMn_(4-x)N 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 Co_(0.8)Mn_(3.2)N is suitable for application to current-induced domain-wall motion devices.