First-principles study of magnetization reorientation and large perpendicular magnetic anisotropy in CuFe2O4/MgO heterostructures

Herein, using first-principles calculations we predict magnetization reorientation and large perpendicular magnetic anisotropy (PMA) in spinel ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$/MgO heterostructure by replacing the octahedral Fe ions with Cu. The substitutional ${\mathrm{Cu}}^{2+}$ ions prefer the octahedral site within the xy-plane layer in an inverse spinel structure, which is associated with the Jahn-Teller tetragonal and $xy$-plane twisted distortions. While magnetization of ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$/MgO is significantly reduced in ${\mathrm{CuFe}}_{2}{\mathrm{O}}_{4}$/MgO, the presence of the substitutional ${\mathrm{Cu}}^{2+}$ ions reorients magnetization from an in-plane to perpendicular magnetic anisotropy. More remarkably, PMA further increases gradually with the film thickness of ${\mathrm{CuFe}}_{2}{\mathrm{O}}_{4}$ layers in the ${\mathrm{CuFe}}_{2}{\mathrm{O}}_{4}$/MgO heterostructure. The underlying mechanism for this large PMA is the interplay of the spin-orbit-coupled Cu ${d}_{xy}--{d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ states in the center layers and the Fe ${d}_{{z}^{2}}$--O ${p}_{z}$ hybridization at the interface. These findings point toward the feasibility of reducing magnetization and enhancing PMA in spinel structures for spintronics applications.