Theoretical Study of Magnetic Damping and Anisotropy of Fe/Pd (001) Superlattice

Abstract

The material properties, magnetic damping and anisotropy, which are critical to spin-transfer-torque magnetic random access memory device performance, are theoretically explored for Fe/Pd superlattices deposited in the (001) orientation. Various superlattice geometries at different Fe and Pd layer thicknesses show perpendicular anisotropy. With the inclusion of the shape anisotropy, thin-film structures with an effective anisotropy of $1.4\,\times \, 10^{7}$ erg/cm3 have been observed. The damping is enhanced due to the broken symmetry at the Pd interface. This interfacial contribution increases when more Pd monolayers are deposited in the superlattice. The superlattice damping is relatively smaller than damping ( $\alpha )$ in the L10 phase FePd. The optimized superlattices are 3Fe/3Pd or 3Fe/2Pd: these multilayers have sufficient energy barriers ( $\sim 1$ eV) to maintain thermal stability in very small devices, yet the switching currents are low ( $\! A/cm $^{2})$ and, thus, expected to lower the energy consumption.