Magnetic properties of cobaltites doped with chromium, gallium, and iron ions

The magnetic and magnetotransport properties of cobaltites La$_{0.5}$Sr$_{0.5}$Co$_{1-x}$Me$_{x}$O$_{3}$ ($Me$ = Cr, Ga, Fe) have been studied. The initial compound ($x$ = 0) is a ferromagnet with $T_C$ = 247 K and a saturation magnetization close to 2$\mu_{\operatorname{B}}$ per formula unit. It has ben shown that chromium substitution ($x$ = 0.2) decreases the spontaneous magnetization to 0.3$\mu_{\operatorname{B}}$, while the iron substitution ($x$ = 0.2) does not change the magnetization. The obtained data have been interpreted in a model of positive superexchange interactions between cobalt and iron and negative superexchange interactions between cobalt and chromium.