Measurement of dielectric properties at low temperatures: application to the study of magnetoresistive manganite/ insulating oxide bulk composites

摘要

In this paper, we report low temperature dielectric measurements of bulk compositeelectroceramic samples containing a colossal magnetoresistive (CMR) manganite phase(La0.7Ca0.3MnO3 [abbreviated LCMO]) and an insulating phase (Mn3O4). Details of theexperimental system are given and possible experimental artefacts due to moisture are outlined.For a LCMO volume fraction of ~ 16%, the permittivity of the LCMO/ Mn3O4 composite atT = 50 K is found to be much higher than that of pure Mn3O4 and magnetic field dependent.This effect is related to an extrinsic space charge polarization mechanism between theinsulating phase (Mn3O4) and the conducting magnetoresistive phase (LCMO).