Specific Heat Experiments at the Cooperative Jahn‐Teller Transition in the Mixed Crystal Systems (Tb_<i>x</i>, Tm_1−<i>x</i>)AsO₄ and (Tb_<i>x</i>, Tm_1−<i>x</i>)VO₄

Abstract

Abstract Single crystals of the systems (Tb x , Tm 1− x )AsO 4 and (Tb x , Tm 1− x )VO 4 are investigated by means of specific heat measurements in the temperature region 1 to 40 K. Whereas for the arsenate a cooperative Jahn‐Teller distortion is observed over the whole concentration range x , in the vanadate the phase transition is missing for 0.1 ≦ x ≦ 0.4. This can be understood in mean field theory taking into account the effect of local strains which are assumed to have a random (Gaussian) distribution.