Decoupled tetracritical points in quenched random alloys with competing anisotropies

The phase diagram of a quenched random alloy of two components with competing anisotropies exhibits two critical lines, corresponding to ordering of only m1 (or m2) spin components. The two lines meet at a tetracritical point, where all m=m1+m2 components order simultaneously. General scaling arguments are used to show that the critical behavior at this point is decoupled, i.e., the m1- and m2-component subsystems have separate scaling free energies. Applications and experiments are briefly discussed.