SPECIFIC-HEATS OF RARE-EARTH IONS IN CRYSTALLINE AND GLASSY PHOSPHATEMATRICES

Measurements have been made of the low-temperature specific heats of l anthanide metaphosphate glasses R(PO3)(3) where R is Gd3+, Dy3+, Pr3+, Sm3+, EU3+ Or La3+. A magnetic contribution to the specific heat of t he glasses modified by Gd3+ and Dy3+ has been found in the temperature region below 7 K. This magnetic specific heat has a T dependence cons istent with the high temperature tail of a Schottky anomaly. The glass containing Pr3+ ions shows excess contributions to the specific heat and to the low-frequency Raman scattering, which are associated with a very large density of low-lying magnetic excitations. To examine the influence of the topological disorder in the glassy state on the magne tic contributions to the calorimetric characteristics, results are com pared and contrasted with those for single-crystal PrP5O14.