Hopping conduction and spin glass behavior of La2FeMnO6

Abstract

We report the existence of a charge localized state in a distorted, low-temperature phase of the perovskite La2FeMnO6 below a charge localization temperature (TCL) ∼133 K, from the detailed analysis of dc resistivity, supported by magnetic and specific heat capacity measurements. We observe that variable range hopping conduction is active below TCL while small polaron hopping conduction governs dc transport both above and below TCL, however with different activation energies. Evidence for the presence of Fe2+ is obtained from the X-ray photoelectron spectroscopic analysis, along with Fe3+, Mn3+, and Mn4+ ions which eventually result in various types of magnetic exchange interactions within the system. As a result, La2FeMnO6 exhibits a spin glass state, which is confirmed by ac susceptibility measurements, zero-field cooled memory and aging tests.