Jahn-Teller driven perpendicular magnetocrystalline anisotropy in metastable Ruthenium

TL;DR

This study discovers a metastable bct-Ruthenium phase with exceptionally large perpendicular magnetocrystalline anisotropy driven by Jahn-Teller effects and orbital interactions, surpassing typical 3d metals.

Contribution

It reveals a new metastable phase of Ruthenium exhibiting unprecedented PMCA driven by Jahn-Teller effects and orbital level reversal.

Findings

PMCA energy as high as 150 μeV/atom

Magnetism governed by Jahn-Teller split eg orbitals

MCA determined by interplay of d_{x^2-y^2} and d_{z^2} states

Abstract

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.