AN ANALYSIS OF THE MAGNETIC GROUND-STATE IN YTTRIUM IRON GARNETS

We analyse the magnetic phase diagram of yttrium iron garnet (YIG) at T = OK (in the MFA approximation) described by a Heisenberg Hamiltonia n. There are Ave different phases and one spin-flop line. Two of these phases are of different semi-spin-glass type. In order to adequately describe them we introduce two new notions: the correlation density fu nction and the information entropy qi the correlation density function s. The functions and their entropies are calculated by means of a Mont e Carlo method. We discovered that the ferrimagnetic point of the phas e diagram corresponding to real YIG falls in the area where three diff erent phases converge. One of these phases is of semi-spin-glass type. The results obtained can shed light on the interpretation of the low- temperature properties of YIG doped with charge uncompensated ions, fo r example Ca2+.