Spin-Resolved Contribution to Perpendicular Magnetic Anisotropy and Gilbert Damping in Interface-Engineered Fe/MgAl2 O4 Heterostructures

The coexistence of a low magnetic Gilbert damping constant and large perpendicular magnetic anisotropy (PMA) in ferromagnetic thin films is critical for high-speed and energy-efficient spintronics devices. To clarify the spin-resolved contributions of damping and PMA, a flat, lattice-matched interface is developed in an Fe(0.7 nm)/MgAl2O4(oxide)(3 nm) bi-layer film by varying the ex situ annealing temperature, which acts as a catalyst to vary the PMA energy densities according to the oxidation degree. Here, the optimized procedure for interface engineering is implemented to achieve an extremely low magnetic Gilbert damping constant (0.013) and a strong interfacial PMA energy (0.8MJm-3) for epitaxial thin films. By employing different interfacial atomic configurations in a first-principles calculation, this study explains the origin of the PMA energy and damping constant. The d(yz) and d(zx) orbitals of the interfacial Fe atoms in the minority-spin states play a role in the orbital moment and its anisotropy. Furthermore, the matrix elements between these two orbitals in the non-spin-flip term predominately contribute to damping. These detailed findings provide a clear insight into the development of materials with significantly improved PMA energies and low damping characteristics, thereby facilitating promising future spintronic applications.