[en] We analyse the magnetic phase diagram of yttrium iron garnet (YIG) at T 0 K (in the MFA approximation) described by a Heisenberg Hamiltonian. There are five 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 function and the information entropy of the correlation density functions. The functions and their entropies are calculated by means of a Monte Carlo method. We discovered that the ferrimagnetic point of the phase diagram corresponding to real YIG falls in the area where three different 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, for example Ca²⁺. (author)