Study of Multiglass state in some pyrochlore oxides.

Abstract

Multiferroics are materials in which magnetism and ferroelectricity coexist. They are of fundamental interest to understand how magnetic ordering can affect electric dipolar ordering and vice-versa. Moreover, they are of applied interest because they allow various types of novel magnetic and electric device structures. A variant of multiferroic materials called multiglass has also been reported ; in which both the magnetic and polar orders are frozen. A multiglass is characterised by the coexistence of a magnetic spin glass and a dielectric glass phase . A thermodynamic glass transition is observed only in the materials with quenched disorder but experimentally, it is observed that some of the disorder-free pyrochlore materials manifest spin glass transition , which is identical to the conventional one with quenched disorder. Very recently, dynamical simulations have been used to suggest that this class of disorder-free pyrochlores could harbour a manifestation of a spin-orbital glass state, a phenomenon characterized by the divergence of the non-linear magnetic and dielectric susceptibilities .This would implicitly mean that these geometrically frustrated pryochlores are multiglasses. This project was aimed to investigate the potential multi-glass state in two pyrochlore oxides; Y2Mo2O7 and Pr2Ru2O7. These specimens synthesized using the solid state ceramic route were evaluated using a combination of structural characterization tools, as well as linear and nonlinear dielectric and magnetic susceptibility measurements.