Propriedades eletrônicas do monocalcogenetos de Sm e de ligas do tipo Sm1-xMxS

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

1981

RESUMO

We present a theoretical model to explain the valence transitions of Sm in Sm1-xMxS alloys, where M is a transition metal (e.g. Y or La) as a function of the concentration x. The system is described by a two-band model: a zero width band of energy E0 (the 4f-level of Sm) and a conduction band, which is treated in the coherent potencial approximation (CPA). The 4felectrons interact between them via a finite intra-atomic coulomb repulsion U, which splits the f-band in two sub-bands at energies E0 and Eo+U. The f -and conduction bands hybridize, being V the hybridization parameter. Within this model it is possible to obtain a continuous valence transition from a non- -magnetic to a non-magnetic or a magnetic ground-state, varying the ratio U/V. The change of valence as a function of pressure in the Sm monochalcogenides (x =0) is also computed. The model used is an extension of the one described above, in which we include a Coulomb repulsion G between f - and conduction electrons, preserving the finite value of U. For different values of G/V we obtain first or second order transitions from a semiconducting to a metallic state. The electrical resistivity in both fases as a function of temperature is also computed and the theoretical results obtained are in good agreement with the experimental ones.

ASSUNTO(S)

fisica da materia condensada compostos de valencia mista susceptibilidade magnetica efeito mossbauer raios x medidas fisicas metodos de funcoes de green densidade de estados eletronicos terras raras altas temperaturas pressao estrutura de bandas

ACESSO AO ARTIGO

Documentos Relacionados