Manipulation of saturation magnetization and perpendicular magnetic anisotropy in epitaxial C o x M n 4 − x N films with ferrimagnetic compensation

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 $\\mathrm{C}{\\mathrm{o}}_{x}\\mathrm{M}{\\mathrm{n}}_{4\\ensuremath{-}x}\\mathrm{N}$ film. We have grown $\\mathrm{C}{\\mathrm{o}}_{x}\\mathrm{M}{\\mathrm{n}}_{4\\ensuremath{-}x}\\mathrm{N}$ films with various Co/Mn ratios on $\\mathrm{SrTi}{\\mathrm{O}}_{3}(001)$ 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 $x\\ensuremath{\\ge}1.1$. The saturation magnetization ${M}_{S}$ decreases as $x$ increases and reaches a minimum value of $15\\phantom{\\rule{0.16em}{0ex}}\\mathrm{emu}/\\mathrm{c}{\\mathrm{m}}^{3}$ at $x=0.8$. Then, it increases with $x$ when $0.8\\ensuremath{\\le}x\\ensuremath{\\le}3.6$ and saturates. These results indicate that ${M}_{S}$ and magnetic anisotropy of $\\mathrm{C}{\\mathrm{o}}_{x}\\mathrm{M}{\\mathrm{n}}_{4\\ensuremath{-}x}\\mathrm{N}$ 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 $\\mathrm{C}{\\mathrm{o}}_{0.8}\\mathrm{M}{\\mathrm{n}}_{3.2}\\mathrm{N}$ is suitable for application to current-induced domain-wall motion devices.