High Frequency dielectric anomaly with charge/orbital ordering of Pr0.5Ca0.5MnO3-δ

Electromagnetic response of Pr0.5Ca0.5MnO3-δ at 34 GHz was measured by a cavity perturbation method in the temperature range from 4.2 to 270 K under the magnetic field up to 5 T. Clear anomalies in the temperature dependence of both the resonant frequency and the full width at half-maximum (FWHM) of Q-curves were observed at the charge/orbital-order phase transition of Pr0.5Ca0.5MnO3-δ. The anomalies of the microwave losses suggest the effect of the depolarization peak due to a large variation of the resistivity with the charge ordering. The dielectric anomalies may be related to a redistribution of charges at the transition related to the orbital ordering. (author)