The quadratic Holstein-Primakoff spin-wave Hamiltonian for three-sublattice Heisenberg systems with different exchange constants (J(ab)=J(bc)not equal J(ca)) was diagonalized by a three-step procedure. The classical ground state was examined and the effects of quantum fluctuation on the ground state were discussed. The 0 K spin reorientation angles due to quantum fluctuations were found to originate from the asymmetry of the system. As an extended application of the spin-wave study of the multisublattice systems, the spin-wave spectra of a Heisenberg superlattice, which has four or three magnetic atoms or spins, in each magnetic unit cell in the x direction, were solved analytically in terms of creation and annihilation operators. It has been found that the spin-wave spectra of the present superlattice systems depend on the exchange constants J and J(1), and that the degeneracy of the spin-wave spectra remains for the superlattice of four atomic layers and is partially removed for the superlattice of three atomic layers mainly due to the asymmetry of the system. Another type of splitting of the energy level occurs which differs for those levels with different degeneracies. The mixing of the interface and the bulk modes were found for the spin-wave dispersion of the superlattices. It was predicted that even for different superlattices having the same exchange constants (either J or J'), i.e., without the oscillation of the exchange coupling, the asymmetry can lead to the oscillation of magnetic properties, such as magnetization and giant magnetoresistance.
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. Spin waves in several Heisenberg systems: Three-sublattice with different exchange constants (J(ab)=J(bc)not equal J(ca)) and a superlattice with the elementary unit of four or three different layers[J]. Physical Review B,1997,55(18):12408-12423.
APA
Z. D. Zhang.(1997).Spin waves in several Heisenberg systems: Three-sublattice with different exchange constants (J(ab)=J(bc)not equal J(ca)) and a superlattice with the elementary unit of four or three different layers.Physical Review B,55(18),12408-12423.
MLA
Z. D. Zhang."Spin waves in several Heisenberg systems: Three-sublattice with different exchange constants (J(ab)=J(bc)not equal J(ca)) and a superlattice with the elementary unit of four or three different layers".Physical Review B 55.18(1997):12408-12423.
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