Large magnetic anisotropy and tunneling anisotropic magnetoresistance in layered bimetallic nanostructures: Case study of Mn/W(001)

Abstract

We predict large magnetic anisotropy energy (MAE) and tunneling anisotropic magnetoresistance in bimetallic $3d\text{\ensuremath{-}}4(5)d$ transition-metal structures which properly balance conditions to maximize moment on the magnetic $3d$ atom, exchange coupling between the $3d$ and $4(5)d$ elements, and magnetic susceptibility and spin-orbit coupling of the $4(5)d$ metal. Our ab initio MAE value of 5.57 meV/Mn atom and relative density-of-states anisotropies of $\ensuremath{\sim}100%$ in the ferromagnetic state of Mn overlayer on W(001) surface demonstrate that the optimal structures may contain unconventional combinations of transition metals. Results are interpreted by employing element and layer specific torque calculations of the MAE. It is shown that large MAE mainly comes from itinerant $5d(\text{W})\text{-atom}$ magnetic moments at the interface and subinterface which are induced by exchange coupling with localized $3d(\text{Mn})\text{-atom}$ moments. To relate these highly anisotropic transition-metal structures to potential applications we also provide estimates of the Curie temperature and the magnetic recording density that can be achieved for system parameters corresponding to our model ferromagnetic Mn/W(001) structure.