Jahn-Teller driven perpendicular magnetocrystalline anisotropy in metastable ruthenium

A metastable phase of body-centered-tetragonal ruthenium (bct Ru) is identified to exhibit a large perpendicular magnetocrystalline anisotropy (PMCA), whose energy E-MCA is as large as 150 mu cV/atom, which is two orders of magnitude greater than those of 3d magnetic metals. Further investigation over the range of tetragonal distortion suggests that the appearance of magnetism in the 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)(-y)(2)(2)and d(z)(2) states, as a result of level reversal associated with tetragonal distortion.