Jahn-Teller type structural phase transition for dysprosium-potassium double tungstate

The low temperature phase transitions in the KDy(WO4)2 single crystal have been studied by ESR and specific heat C(T) methods. Both the broad maximum of C(T) with peak at Tc equals 6.38 K and (lambda) -shaped temperature dependence of the ESR line width (Delta) H(T) in the vicinity of the transition may be explained as being due to the structural phase transition. The analysis of C(T) and (Delta) H(T) dependences show that the second order structural phase transition observed at Tc equals 6.38 K is the transition of Jahn-Teller type and does not occur with a change of point symmetry. The phase transition observed at about 0.6 K for heat capacity is connected with magnetic order of dysprosium ions.