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Prog. Theor. Phys. Vol. 60 No. 3 (1978) pp. 646-660
Surface Effect on Thermodynamic Properties and Excitation Spectra of Heisenberg Ferromagnets
Osamu Sakai,
Hiroshi Kurita and
Masashi Tachiki
The Research Institute for Iron, Steel and Other Metals, Tohoku University, Sendai 980
(Received November 4, 1977)
Abstract:
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 Js between spins on the surface is considerably large compared with the bulk exchange constant, the surface magnetization vanishes at the bulk Curie temperature Tc. The spin-ordered state at the surface becomes unstable above Tc 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 Js, and when Js is large it is much larger than the bulk susceptibility.
URL :
http://ptp.ipap.jp/link?PTP/60/646/
DOI : 10.1143/PTP.60.646
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