GLASSY PROPERTIES OF DILUTE DIPOLAR ISING SYSTEMS

Dilute dipolar Ising systems are studied within the local mean field approximation. The phase diagram on the temperature-dilution plane consists of four phases: ferromagnetic, spin glassy, mixed, and paramagnetic. Many similarities to results of experiments on LiHoxY1-4F4 are found except for the absence of a paramagnetic phase at T = 0. The glassy phase is characterized by a domain structure. An exact ennumeration of states in small clusters shows that the number of local energy minima in dipolar systems grows exponentially with the number of spins.