The compensation temperature of a mixed spin-1/2 and spin-1 Heisenberg ferrimagnetic systems

In this paper, we investigate the compensation point of the ferrimagnetic systems described by Heisenberg Hamiltonian with exchange anisotropy instead of single-ion anisotropy. By constructing four models, with two being two dimensional and other two being three dimensional, the impact of the parameter in Hamiltonian on the compensation temperature is discussed. The conditions for the compensation point, T _com, to appear are investigated in detail. The exchange interactions between the spins inside the sublattice with the smaller and larger spin quantum numbers are denoted by J _aa and J _bb, respectively. In the presence of exchange anisotropy, the necessary condition for T _com to appear is that the ratio $J_{aa}/J_{bb}$ should be beyond some value that depends on J _bb. In three-dimensional systems, the Hamiltonians can be isotropic. These conclusions stand for both the Néel and collinear structures. (paper)