Quantum effects in an anisotropic ferrimagnet

Temperature dependence of static and dynamic properties of an anisotropic ferrimagnet

“…However, the single ion anisotropy will have an effect on the temperature behavior of the second sublattice, because the expres sion for the average magnetic field includes . The system of equations (4) and (5) is substantially nonlinear and amenable to analytical treatment only for low temperatures [11,12]. It can be seen from these figures that, at low tem peratures, there is almost no difference between the isotropic and anisotropic cases.…”

“…where J (i) > 0, i = 1, 2, and J (12) < 0 are the exchange interaction constant in the first sublattice, the exchange interaction constant in the second sublat tice, and the intersublattice interaction constant, respectively; S n is the spin operator of the first sublat tice; s l is the spin operator of the second sublattice; n and l are the numbers of sites of the first and second sublattices, respectively; β > 0 is the single ion anisot ropy constant, which describes the easy plane anisot ropy; and the easy plane is the ZOY plane. The z axis is chosen as the quantization axis; in this case, the spin of the first sublattice (per site) 〈S〉 is aligned parallel to the z axis, i.e., 〈S z 〉e z , and the spin of the second sub lattice 〈s〉 is aligned antiparallel to this axis.…”

“…One of the most significant manifestations of the effect of quantum spin reduction is the appearance of an additional branch of spin fluctuations, which is characterized by oscillations of the average value of the spin in magnitude [12]. We are interested in the situa tion where the single ion anisotropy constant is sub stantially smaller than the exchange interaction con stant and in which it should be expected that the fre quency of this mode will be sufficiently high.…”

“…Recently, it has been shown that, at a low temperature, the effect of quantum spin reduction is strongly suppressed as a result of the influence exerted by the exchange field of the isotropic sublattice on the anisotropic sublattice [12]. However, it can be expected that, at a significant temperature, when the magnetization and the exchange field of the isotropic sublattice are not very strong, the effect of quantum spin reduction of the anisotropic sublattice will have a substantial influence on the magnetic properties of the magnet.…”

“…This can be achieved using the algebra of the Hubbard operators [10,12,13], which are related to the spin operators as follows:…”