Effect of single-ion uniaxial anisotropy on the phase diagrams of magnetic system in the presence of internal spin fluctuation

A comprehensive study of Heisenberg-like systems with internal spin fluctuation

“…J 0 is on-site exchange. The last two terms represent single-ion anisotropy [4]. In equation ( 1), the subscripts a and b label the two sub-lattices and the summation (ia, jb) means that the summation is taken over all the nearest neighbour pairs.…”

“…In equation ( 1), the subscripts a and b label the two sub-lattices and the summation (ia, jb) means that the summation is taken over all the nearest neighbour pairs. In this paper the sub-spin quantum numbers for the two sub-lattices are taken as the same, that is to say, We let the exchange parameters be dimensionless as in [3][4][5]. The method we use is the many-body Green function theory which has long been used to treat the Heisenberg exchange model [3,[6][7][8].…”

“…coupling parameters J 1 and J 2 are fixed. We also copy the results by MFT [4]. It is obvious that the MFT overestimates the Curie point.…”

“…Note that in either state A or B, the system is ferromagnetic. In [4], the cases with parameters J 1 = 1, J 2 = 0.5 and J 0 = 0.2 and J 3 < 0, which are state B here, were thought to Table 1. Parameters that the phase diagrams in figure 2 have.…”

“…They studied the spontaneous magnetization and susceptibility of ferromagnetism described by such a Hamiltonian by the many-body Green function method. Jiang et al [4] added a uniaxial anisotropy term to study its effect on the system, especially the shift of Curie point, by mean-field theory (MFT). Both of the works merely studied the ferromagnetic state.…”