A spectacular pressure-induced electronic transition in KTb(MoO₄)₂

Abstract

Results of pressure Raman and optical absorption studies are reported for KTb(MoO₄)₂. A phase transformation occures at 27kbar when the crystal is pressurized at ambient temperature, in a hydrostatic pressure medium. The sample changes to a deep yellow colour at the transition and visibly contracts in the a-axis direction. The colour shifts red on further pressure increase. The Raman spectral features and the X-ray powder pattern change abruptlu at the transition indicating a structural change. The colour change is attributed to 4f-5d transition in Tb initiated by the structural transition, and consequent intervalence charge transfer between Tb and Mo.