Theory of magnetic behaviour in calcium-doped yttrium iron garnet

Properties of the Semi Spin Glass Ground State of Garnets

“…The other regions of the phase plane are described in Ref. [1]. In order to learn more about the magnetic properties of the system in these phases, we examine the magnetic structure factor, the spectrum of magnetic excitations, the magnetic specific heat and the density of states at different but relatively close points of the semi spin glass phase (A, B, C, D, and F as indicated in the inset in Fig.…”

“…An analysis of the phase diagram of YIG performed in the classical limit [1] (see the inset in Fig. 1), indicates the occurrence of the semi spin glass phases AF-I and AF-II.…”

“…It seems to be challenging to propose a new model which could explain at least some of the changes. Recently we have concentrated on an analysis of the change in magnetic properties which is displayed by YIG on the valence-uncompensated doping.As known, pure YIG is an insulating ionic crystal with ferrimagnetic collinear order.Magnetic properties of the system can be studied with the two-sublattice Heisenberg Hamiltonian [1,2] S is the S = 5/2 iron spin operator localized either at the sites of the octahedral (i, j) or tetrahedral (k,1) sublattice. Both the intra-and inter-sublattice coupling constants are limited to nearest neighbours, only, and denoted by J a , Jd and Jad, respectively.…”

“…Magnetic properties of the system can be studied with the two-sublattice Heisenberg Hamiltonian [1,2] S is the S = 5/2 iron spin operator localized either at the sites of the octahedral (i, j) or tetrahedral (k,1) sublattice. Both the intra-and inter-sublattice coupling constants are limited to nearest neighbours, only, and denoted by J a , Jd and Jad, respectively.…”

“…[1]) which is applied to N, = 40 spins of an elementary unit cell with the periodic boundary conditions imposed on the superexchange interactions by translational invariance of the Hamiltonian. The quantum fluctuations, however, are neglected in our calculations and the Hamiltonian is replaced by its classical analogon, which actually means that all the spin operators are replaced by the classical vectors Sni.…”