Graduate student Nenian Charles and Professor Rondinelli report on the microscopic origins of symmetry-preserving transition in fluoromangates. The article appearing in Physical Review B and titled, Microscopic origin of pressure-induced isosymmetric transitions in fluoromanganate cryolites, describes how hydrostatic pressure induces a reorientation of the Mn-F Jahn-Teller bond axis in the fluoride cryolite Na3MnF6.
Remarkably, unlike the perovskite oxide manganates, the Jahn-Teller distortion of the Mn3+ cation persists both before and after the isosymmetric phase transition. The strong orbital-lattice coupling facilitates the electronic transition, which is marked by a giant (70%) change in the orbital polarization of the Mn eg manifold through a renormalization of the mode stiffness of the JT distortion. Uncovering the microscopic origins of the transition sheds light on the effect of stress on the magnetic, electronic, and structural degrees of freedom in manganates—and importantly, the more ionic fluorides can display as exciting physics as the oxides.