ESR-STUDY OF THE LOW-TEMPERATURE PHASE-TRANSITION IN KDY(WO4)(2)

The low-temperature structural phase transition of the Jahn-Teller typ e in a KDy(WO4)(2) single crystal has been studied by means of the ESR method. The ESR line width near the point of transition (T-spt approx imate to 7 K) is shown to increase from 0.17 T up to a maximum value o f 0.24 T and then it decreases to 0.19 T. The width of transition area is about 8 K. The symmetry of g-tensor does not change at the point o f the phase transition while the values of the g-tensor components cha nge considerably: g(z) = 3.13; g(x) approximate to 0; g(y) = 0.82 at T > T-spt; g(z) = 1.98; g(x) approximate to 0; g(y) = 1.19 at T < T-spt . It is suggested that the symmetry of high-and low-temperature phases is identical.