PHASE-DIAGRAM FOR A MODEL EXCHANGE-DISORDERED MAGNETIC ALLOY - PHYSICAL PRINCIPLES

The mean-field phase diagram for an XY model on a square lattice is studied. At low temperatures, noncollinearity can be produced by individual "strong" impurity bonds or a finite concentration of "weak" impurity bonds. Thermal fluctuations tend to destroy this noncollinearity, leading to a collinear state at low enough impurity concentrations. For both "weak" and "strong" impurities the phase diagram has a multicritical point like that found by Gabay and Toulouse. However, "very strong" impurity bonds lead to noncollinearity at all temperatures where there is magnetic order, and yield a phase diagram with a multicritical point unlike that of Gabay and Toulouse.

PHASE-DIAGRAM FOR A MODEL EXCHANGE-DISORDERED MAGNETIC ALLOY - PHYSICAL PRINCIPLES Academic Article