Electronic and magnetic phase diagram of La0.5Sr0.5Co1-xFexO3 (0 <= x <= 0.6) perovskites

Abstract

Spin dynamics and magnetic frustration effects in La0.5Sr0.5Co1-xFeO3 (0 <= x <= 0.6) compounds were systematically studied by means of resistivity, dc magnetization, ac susceptibility, and electron-spin-resonance spectra. The Fe substitution caused a metal-semiconductor transition for x <= 0.3 compositions whereas the only semiconducting state behaved for x > 0.3 compositions. With increasing Fe-doping levels, the ferromagnetic-paramagnetic transition temperature, T-C, decreased from 250(x=0) to 166 K (x=0.4). Aspin-glass behavior was observed for x > 0.4 compositions and is attributed to the frustration of random competing exchange interactions, namely, the ferromagnetic Co3+-CO4+ double-exchange interaction and the antiferromagnetic interactions such as Co-O-Fe and Fe-O-Fe. The internal dynamic properties of the samples were elucidated by the,electron-paramagnetic-resonance spectra. An electronic and magnetic phase diagram of La0.5Sr0.5Co1-xFexO3 is drawn up. (c) 2005 American Institute of Physics.