Crucial role of interlayer distance for antiferromagnet-induced perpendicular magnetic anisotropy

Antiferromagnetic (AFM) thin films were recently proposed to be an alternative to conventional materials for achieving perpendicular magnetic anisotropy (PMA) in ferromagnetic thin films, because AFM thin films exhibit an advantage of flexible control. Here, we report that antiferromagnet-induced PMA is highly sensitive to interfacial moments of AFM thin films as well as the magnetic interaction of such moments with volume moments, determined according to the vertical interlayer distance. Magnetic hysteresis loops and x-ray magnetic domain imaging revealed the establishment of perpendicular magnetization on face-centered tetragonal (fct)-like Mn/Co/Ni films when covered with monolayered Mn films. A cover of Mn films that exhibit contracted fct- [vertical-to-in-plane lattice constant ratio $(\mathrm{c}/\mathrm{a})=0.95]$ and expanded fct-like $(\mathrm{c}/\mathrm{a}=1.05)$ structures at different thickness levels induced in-plane magnetic anisotropy and PMA in Co/Ni films, respectively, confirming that the interlayer distance is a crucial parameter for establishing perpendicular magnetization.