Magnetic Structures in Spinel B-Site Lattices; A Proposal of Linear Antiferromagnetism in ZnMn₂O₄

Abstract

A microscopic molecular field theory has been applied to the B-site lattices of the spinel structure (tetragonal or cubic). It has been found that one of the following three spin configurations has the lowest energy depending on the relative strength of exchange interactions: (i) “antiferromagnetic line structure”, (ii) “Verwey order type structure”, and (iii) Pure ferromagnetic structure. Our experimental results on ZnMn 2 O 4 , described in this paper, suggest that the “antiferromagnetic line structure” is realized in this oxide. The effect of exchange interactions other than the nearest neighbour ones has also been discussed with special attention to the spin configuration in GeNi 2 O 4