Magnetic Transitions in Cubic Spinels

Abstract

Magnetization curves of the cubic spinels MnCr₂O₄, CoCr₂O₄, MnV₂O₄, and CoV₂O₄ have been obtained between 4.2°K and their Curie points. With the possible exception of MnV₂O₄, all the curves indicate the presence of a magnetic transition within this temperature range. Although all these materials have been reported to be normal spinels, inconsistencies between our results and the recent theory of spin configurations in normal cubic spinels led to further experiments which established that CoV₂O₄ is not, in general, normal. Theory suggests the presence of two types of transition in MnCr₂O₄ and CoCr₂O₄, but only one has been observed in each case. The temperatures at which the observed break in the magnetization curves of these materials occurs can be interpreted by ascribing them to different types of transitions. The interpretation of the MnCr₂O₄ magnetization curve is compatible with the neutron diffraction results of Corliss and Hastings.