Enhanced voltage-controlled magnetic anisotropy via magnetoelasticity in FePt/MgO(001)

The interplay between magnetoelectricity and magnetoelasticity (MEL) is studied in the context of voltage-controlled magnetic anisotropy (VCMA). Strain plays more than the role of changing lattice constants---that of the internal electric field in the heterostructure. As a prototype, FePt/MgO(001) is visited, where the behavior of two interfaces are drastically different: one exhibits switching, the other does not. Whether an external electric field (${E}_{\text{ext}}$) is present or not, we found the VCMA coefficient larger than $1\phantom{\rule{0.16em}{0ex}}\mathrm{pJ}/(\mathrm{V}\phantom{\rule{0.16em}{0ex}}\mathrm{m})$ as a consequence of the rearrangement of $d$ orbitals with $m=\ifmmode\pm\else\textpm\fi{}1$ and $\ifmmode\pm\else\textpm\fi{}2$ in response to an external electric field. In addition, magnetocrystalline anisotropy is analyzed with strain taken into account, where a nonlinear feature is presented, only accountable by invoking second-order MEL.