Surface Effect on Thermodynamic Properties and Excitation Spectra of Heisenberg Ferromagnets

概要

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Tyablikov's method is applied to Heisenberg ferromagnets with surface. The magnetization, the excitation spectrum and the magnetostatic susceptibility near the surface are calculated. Calculations show that even when the exchange constant J_s between spins on the surface is considerably large compared with the bulk exchange constant, the surface magnetization vanishes at the bulk Curie temperature T_c. The spin-ordered state at the surface becomes unstable above T_c owing to the thermal excitations to the levels with a finite density of states at ω=0. Bound states localized near the surface appear in the excitation spectra. The magnetostatic susceptibility at the surface is very sensitive to the magnitude of J_s, and when J_s is large it is much larger than the bulk susceptibility.
理論物理学刊行会の論文
1978-09-25