Effect of Excitonic Correlations on Magnetic Order in Mixed Valence 4f-Systems
An attractive interaction between conduction electrons and 4f-holes has been incorporated into the periodic Anderson model (PAM). This model Hamiltonian has been approximated by the full mean-field decoupling of the electron-hole interaction and also the 4f Coulomb repulsion. The approximated Hamiltonian is in fact a renormalized PAM where the coupling constants themselves contain terms like average f−, d−, level occupations n1 and nd respectively and the excitonic correlation <d+ iσfiσ> = γσ which have to be determined self-consistently. The Curie temperature Tc has been studied as a function of the 4f-level position Ef for a fixed Bloch band width W for different values of the particle-hole attractive strength Ufd. The presence or absence of excitonic correlations does not seem to affect the qualitative behaviour of Tc as a function of Ef. However, the presence of Ufd, and γσ-destabi1ize the long range magnetic order which is reflected as a fall in Tc.
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- 1.S.K. Malik, A.M. Umarji, G.K. Shenoy, A.P. Montano, and M.E. Reeves, Phys. Rev. B31 4738 (1985).Google Scholar
- 4.G. Gangadhar Reddy and A. Ramakanth, to be published in Phys. Stat. Soli. b 138 (1986).Google Scholar
- 5.W. Nolting and A. Ramakanth, Phys. Rev. B33 1838 (1986).Google Scholar
- 6.W. Nolting and A. Ramakanth, to be published in Phys. Stat. Soli. b 139 (1987).Google Scholar