The Hamiltonian for two-sublattice Heisenberg ferromagnets and ferrimagnets with different sublattice anisotropies, which is applicable for rare-earth-transition-metal (R-T) intermetallics, is established. In order to study spin-waves in easy plane or easy cone configuration, a transformation of spin-vector coordinates is performed by rotating the quantization axis frame by Eulerian angles and accordingly the Hamiltonian. Spin-wave spectra at low temperatures of the present system are determined by performing the standard Holstein-Primakoff transformation and a four-step diagonalizing procedure consisting of two coupled Cullen transformations, an extended Bogoliubov transformation, two independent Bogoliubov transformations and two independent Holstein-Primakoff transformations. The results for the ground states of the easy axis, the easy plane and the easy cone configurations are compared with those obtained by the mean-field theory. The border lines between the different spin structures are derived in either the purr classical limit or the large-exchange limit. Continuous transitions, accompanied with the continuous change of the angle between the averaged sublattice magnetizations, are found in both cases. It is found that splittings of the spin-wave spectra of the two-sublattice Heisenberg ferromagnets or ferrimagnets exist. A gap can appear in the spin-wave spectra, depending on the competition among the exchange and the anisotropies. Other physical properties, such as sublattice magnetization and specific heat, are discussed also.
部门归属
acad sinica,int ctr mat phys,shenyang 110015,peoples r china.;zhang, zd (reprint author), acad sinica,inst met res,wenhua rd 72,shenyang 110015,peoples r china
Z. D. Zhang,T. Zhao. Spin waves at low temperatures in two-sublattice Heisenberg ferromagnets and ferrimagnets with different sublattice anisotropies[J]. Journal of Physics-Condensed Matter,1997,9(38):8101-8118.
APA
Z. D. Zhang,&T. Zhao.(1997).Spin waves at low temperatures in two-sublattice Heisenberg ferromagnets and ferrimagnets with different sublattice anisotropies.Journal of Physics-Condensed Matter,9(38),8101-8118.
MLA
Z. D. Zhang,et al."Spin waves at low temperatures in two-sublattice Heisenberg ferromagnets and ferrimagnets with different sublattice anisotropies".Journal of Physics-Condensed Matter 9.38(1997):8101-8118.
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