The authors report ab initio total energy calculations on the first-order structural transition of the ferromagnetic MnCo1−xGe intermetallic compound (x = 0 to 0.25). They showed that increasing Co vacancies induce a transition from an orthorhombic structure, at x = 0 to 0.08, to an hexagonal structure at x > 0.08. A concomitant high-to-low moment magnetic transition and a large magnetovolume effect occurred due to the change of the symmetry and the resulting coupling distance between the magnetic atoms. These results provided an excellent account for the experimental results and revealed the crucial role of the Co vacancies in determining the relative structural stability and the magnetic properties of MnCo1−xGe.

Vacancy Induced Structural and Magnetic Transition in MnCo1-xGe. J.T.Wang, D.S.Wang, C.Chen, O.Nashima, T.Kanomata, H.Mizuseki, Y.Kawazoe: Applied Physics Letters, 2006, 89[26], 262504 (3pp)