Magnetoelastic contribution to thermal expansion of rare-earth zircons

Abstract

Comparative analysis is performed for the magnetoelastic contributions to thermal expansion of two groups of rare-earth zircons: phosphates RPO 4 (R=Y,Tb–Yb) and vanadates RVO 4 (R=Pr, Nd, Gd–Yb). Significant magnetoelastic anomalies of thermal expansion are observed and magnetoelastic contributions are found in regard to the corrections for the changes of the phonon contributions throughout the series of RPO 4 and RVO 4. Magnetoelastic contributions to thermal expansion are demonstrated to be well accounted for by the temperature dependences of the quadrupole moments of rare-earth ions both in phosphates and vanadates. The fully symmetric magnetoelastic coefficients are determined for all the rare-earth compounds under investigation; they are of the same sign and comparable magnitude in vanadates and phosphates, whereas the magnetoelastic contributions are opposite in sign for two isomorphous groups of rare-earth zircons.