Decoupled Tetracritical Points in Quenched Random Alloys with Competing Anisotropies

Abstract

The phase diagram of a quenched random alloy of two components with competing anisotropies exhibits two critical lines, corresponding to ordering of only $m_1$ (or $m_2$) spin components. The two lines meet at a tetracritical point, where all $m=m_1+m_2$ components order simultaneously. General scaling arguments are used to show that the critical behavior at this point is decoupled, i.e., the $m_1$- and $m_2$-component subsystems have separate scaling free energies. Applications and experiments are briefly discussed.