Abstract
We present an exactly solvable microscopic model of the T=0 K magnetovolume properties (spontaneous volume magnetostriction, forced volume magnetostriction, compressibility, pressure-induced magnetization response, and paraprocess susceptibility) of a local moment binary alloy with two magnetic species, chemical disorder, and the possibility of magnetic frustration. The calculated properties are shown to have an explicit dependence on both the ground-state spin structure and the degree of magnetic frustration, evaluated as the fraction of magnetic exchange bonds that are energetically not satisfied. We apply this model to fcc alloys (including classical Invar at y=0.35) in which we determine the spin structures by adjusting Monte Carlo simulation results to the measured magnetic properties. We find that Invar () is a highly frustrated system and that this effectively changes the sign of the resulting magnetovolume expansion. Invar alloys based on high-moment γ-Fe are therefore understood as arising from an optimized blend of ferromagnetism, that causes most of the Fe-Fe bonds to be unsatisfied, and the antiferromagnetism of the magnetovolume active Fe-Fe bonds. © 1996 The American Physical Society.
- Received 1 May 1996
DOI:https://doi.org/10.1103/PhysRevB.54.12225
©1996 American Physical Society