Manipulation of saturation magnetization and perpendicular magnetic anisotropy in epitaxial <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi mathvariant="normal">C</mml:mi><mml:msub><mml:mi mathvariant="normal">o</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mi mathvariant="normal">M</mml:mi><mml:msub><mml:mi mathvariant="normal">n</mml:mi><mml:mrow><mml:mn>4</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:mi mathvariant="normal">N</mml:mi></mml:mrow></mml:math> films with ferrimagnetic compensation
Keita Ito, Yoko Yasutomi, Siyuan Zhu, Munisa Nurmamat, Masaki Tahara, Kaoru Toko, Ryota Akiyama, Yukiharu Takeda, Y. Saitoh, Tamio Oguchi, A. Kimura, Takashi Suemasu
Abstract
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.