Abstract
In this paper it is shown that a combined investigation of the magnetic and the semiconducting properties of the solid solutions of LaMnO3 and LaCoO3 is necessary for a complete understanding of this rather complicated system. The conductivity gives information on the valency states of the ions and with this knowledge the magnetic properties become understandable. Mixtures of Mn3+ and Co3+ ions tend to the formation of Mn4+–Co2+ pairs having a positive magnetic superexchange interaction.