"Melting" of Frustrated Spins: Mechanism for Reentrant Ferromagnetic-Spin-Glass Behavior

Abstract

The local mean-field equations are solved for $\mathrm{XY}$ spins on a square lattice with competing nearest-neighbor interactions. For a model with randomly chosen frustrated sites, on lowering the temperature one finds the following sequence of phases: paramagnet; nonuniform ferromagnet; noncollinear, nonuniform ferromagnet; reentrant spin-glass. The reentrant transition occurs via the mechanism of frustrated-spin "melting." For randomly chosen negative bonds it is more difficult to obtain reentrance and to provide a physical explanation.