A new metastable phase of the body-centered-tetragonal ruthenium ({ \em bct}--Ru) is identified to exhibit a large perpendicular magnetocrystalline anisotropy (PMCA), whose energy, $E_{ MCA}$, is as large as 150 $\mu$eV/atom, two orders of magnitude greater than those of 3$d$ magnetic metals. Further investigation over the range of tetragonal distortion suggests that the appearance of the magnetism in the { \em bct}--Ru is governed by the Jahn-Teller spit $e_g$ orbitals. Moreover, from band analysis, MCA is mainly determined by an interplay between two $e_g$ states, $d_{ x^2-y^2}$ and $d_{ z^2}$ states, as a result of level reversal associated with tetragonal distortion.
Categories: cond-mat.mtrl-sci