Accession Number:

AD0405005

Title:

CLASSICAL THEORY OF THE GROUND SPIN-STATE IN NORMAL TETRAGONAL SPINELS. I. NEEL, YAFET-KITTEL, AND COLLINEAR ANTIFERROMAGNETIC MODES,

Descriptive Note:

Corporate Author:

MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB

Personal Author(s):

Report Date:

1962-04-23

Pagination or Media Count:

14.0

Abstract:

An appreciable number of magnetic materials with the spinel structure exhibit tetragonal symmetry, rather than cubic, in their x-ray diffraction patterns. Because of the distortion, five different nearest-neighbor exchange interactions are possible, so that four ratios t, u, v, and w amongst these interactions are required for the characterization of such a material. The generalized Luttinger-Tisza method GLT is used to determine rigorously the ranges of values of the above ratios regions in t, u, v, w parameter space for which the familiar Neel, Yafet-Kittel, and collinear antifenromagnetic spin configura tions k0 modes are the ground states of the classical Heisenberg exchange energy. The ground-state regions are found to be significant ly smaller than would be predicted on the basis of a sublattice model. Consequently, knowledge of the actual spin configuration can place impor tant restrictions upon the relative strengths of exchange interactions, as in the case of copper chromite. In addition, we find that the desta bilizing k vector is not always parallel to a symmetry direction, even for nearly-cubic spinels. Author

Subject Categories:

Distribution Statement:

APPROVED FOR PUBLIC RELEASE