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Title: Collective and intrinsic degrees of freedom in the Heisenberg ferromagnet.
Authors: Providência, João da 
Brajczewska, Marta 
Fiolhais, Carlos 
Keywords: Heisenberg ferromagnet
Issue Date: 1989
Publisher: Institute of Physics
Citation: PROVIDÊNCIA, João da ; BRAJCZEWSKA, Marta ; FIOLHAIS, Carlos – Collective and intrinsic degrees of freedom in the Heisenberg ferromagnet. Journal of physics. A : Mathematical and Theoretical. Bristol : Institute of Physics. ISSN 1751-8113. Vol. 22 (1989), p. 703-715.
Serial title, monograph or event: Journal of physics. A : Mathematical and Theoretical
Volume: 22
Place of publication or event: Bristol
Abstract: A separation between collective and intrinsic degrees of freedom in the Heisenberg model of a ferromagnet at a finite temperature is achieved by reformulating the thermal boson expansion previously obtained by the present authors. In the new approach, all the collective modes (spin waves) have wavenumbers lower than a certain value. The intrinsic energy turns out to be the usual mean-field energy minus a correlation energy due to the excitations of spin waves. The influence of the cutoff in momentum space on the critical temperature is studied and the temperature dependence of the spin-wave renormalisation factor and the magnetisation are calculated.
ISSN: 1751-8113
DOI: 10.1088/0305-4470/22/6/021
Rights: openAccess
Appears in Collections:FCTUC Física - Artigos em Revistas Internacionais

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