Magnetic Properties of Perovskites Containing Strontium

I. Strontium-Rich Ferrites and Cobaltites

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Magnetic susceptibilities and electrical conductivities of (La, Sr)(Fe/Co)O_x samples sintered in vacuo or in oxygen stream are measured here. Samples containing tetravalent magnetic ions in general have Curie contants smaller than those containing only trivalent ions. This fact and the high conductivity in the former specimens strongly support the combined effect of the double exchange and the usual exchange mechanism in these compounds. The parallel alignment of spins of magnetic ions due to double exchange is partly or completely hindered by the presence of the strongly negative trivalent-trivalent interionic interactions.