Mean-field theory of magnetic transitions in semi-infinite Ising models
1985; American Physical Society; Volume: 31; Issue: 11 Linguagem: Inglês
10.1103/physrevb.31.7146
ISSN1095-3795
AutoresF. Aguilera‐Granja, J. L. Morán‐López,
Tópico(s)Spectroscopy and Quantum Chemical Studies
ResumoThe semi-infinite Ising model, for S=(1/2) and with an arbitrary number of surface magnetic couplings ${J}_{\mathrm{mn}}$ different from the bulk J, is solved in the mean-field approximation. Exact expressions for the critical couplings ${J}_{\mathrm{mn}}$,C leading to a surface Curie temperature ${T}_{\mathrm{CS}}$ higher than the bulk ${T}_{C}$ are obtained. The value for ${T}_{\mathrm{CS}}$ in the semi-infinite crystal is obtained by means of a continued-fraction method. The model is applied to explain recent experimental results on the (0001) surface of gadolinium.
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