Electronic and magnetic phase diagram of La 0.5Sr 0.5Co 1-xFe xO 3 (0≤x≤0.6) perovskites

Abstract

Spin dynamics and magnetic frustration effects in La0.5 Sr0.5 Co1-x Fex O3 (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, TC, decreased from 250 (x=0) to 166 K (x=0.4). A spin-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 La0.5 Sr0.5 Co1-x Fex O3 is drawn up. © 2005 American Institute of Physics.