First Observed Metal-like to Insulator Transition in the vacant 3d orbital Quantum Spin Liquid Tb$_2$Ti$_2$O$_7$

Abstract

We report the observation of metal-like to insulator transition (MTI) in the 3dpyrochlore oxide Tb2Ti2O7 at 603 K due to the interaction of empty 3d orbitals of Ti4+ with O2- ions, evidenced by the transition in resistivity. Magnetisation, specific heat capacity and differential scanning calorimetry support the MTI, and the transition is of second order. An appreciable change in magnetisation with temperature, without any magnetic phase transition, is a behaviour typical in this family of compounds which is seldom observed in empty d orbital pyrochlores. The possible mechanism that supports the MTI in Tb2Ti2O7 is discussed. Subsequently, a broad change in magnetisation from 696 K is also seen. Thermogravimetric analysis confirms the observed MTI (603 K) and the broad change in magnetisation (696 K)are not due to oxygen vacancy