Cooperative Jahn-Teller induced phase transition of TbVO₄: single crystal structure analyses of the tetragonal high temperature phase and the twinned orthorhombic phase below 33 K

Abstract

The rare earth vanadate TbVO4, undergoes a crystallographic phase transition below 33 K induced by a cooperative Jahn-Teller effect. Twinning of the crystal occurs upon this transition from the tetragonal high temperature phase to the orthorhombic low temperature phase resulting in a domain structure. Single crystal x-ray analyses of the tetragonal and the twinned orthorhombic phase verify a reduction in the site symmetry of the Tb ion from D2d (m2-dodecahedral) for the high temperature phase to D2 (222-distorted dodecahedral) for the low temperature phase. Concomitantly, the space group symmetry is lowered from D194h (I41/amd) to D242h (Fddd). The twinned orthorhombic phase is described as domains related to each other by a 180° rotation about the orthorhombic [110] axis.

In situhigh-pressure synchrotron x-ray diffraction study of CeVO4and TbVO4up to 50 GPa

“…The refined unit-cell parameters for these phases are a = 7.377(7) Å and c = 6.485(6) Å for CeVO 4 and a = 7.166(7) Å and c = 6.317(6) Å for TbVO 4 . These values are in agreement with earlier reported values [6,14].…”

“…Assuming a zircon-type structure, all the patterns observed between ambient pressure and 4.4 GPa can be well indexed. Earlier a structural transition around 33 K has been reported in temperature dependent studies on TbVO 4 [14]. This structural transition has been assigned to the cooperative Jahn- [3].…”

“…To close this part of the discussion we would like to add that the zircon-schelite-fergusonite sequence found in TbVO 4 does not show any evidence of induction of cooperative Jahn-Teller effects as observed in the phase transitions driven at low temperature [14].…”

Giant magnetic anisotropy and tunnelling of the magnetization in Li2(Li1−xFex)N

“…Insulating samples with diluted or non-interacting magnetic moments have been far less studied-diluted magnetic semiconductors are explicitly excluded from this statement because of their finite carrier density. A possible explanation for the absence of magnetic tunnelling in insulators is a Jahn-Teller distortion, which is frequently observed, for example, in lanthanide zircons of the form RXO 4 (Kirschbaum 39 and references therein). According to the JahnTeller theorem 40 , the orbital degeneracy of Fe should cause a structural distortion also for Li 2 (Li 1 À x Fe x )N in order to reach a stable state.…”

A single-solenoid pulsed-magnet system for single-crystal scattering studies

“…11,12 Flux-grown crystals were ground into a fine powder. The powder was mixed with GE varnish in a circular groove on a thin sapphire plate attached to the end of the sample mount (Fig.…”