| In Fe(II) Fe(III) bimetallic oxalates, the energy scale of the spin-orbit coupling λ and the Jahn-Teller (JT) effect are close to each other. Thus, an interesting interplay between the two effects is expected, for example, by changing temperature. We theoretically predict that an undistorted phase with C3 symmetry about each Fe site may be recovered at low temperatures. Both lower and upper JT transitions bracketing the ferrimagnetic transition temperature Tc are predicted for compounds that exhibit magnetic compensation. Comparisons with recent measurements and first-principles calculations provide strong evidence for the inverse JT transition below Tc. The inverse JT transition is signaled by the jump in the avarage magnetization at T/|λ| ~ 0.25 as shown in the right panel. This work was done by Randy S. Fishman and Satoshi Okamoto in collaboration with Fernando A. Reboredo at MTG, ORNL. Phys. Rev. Lett. 101, 116402 (2008) |
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