paper

Crossover between local-moment magnetism and itinerant-electron magnetism in the t-J model

arXiv:cond-mat/0510377 · doi:10.1143/JPSJ.74.3340

Abstract

A Kondo-lattice theory is applied to the crossover between local-moment magnetism for almost half fillings of electrons and itinerant-electron magnetism away from the half filling. In clean systems with no disorder, the bandwidth W^* of quasiparticles is non-zero and of the order of |J| at T=0K even in the limit of the half filling, with J the superexchange interaction constant between nearest neighbors. The so called Gutzwiller's term also contributes to W^* away from the half filling; it is approximately proportional to doping concentrations measured from the half filling. Magnetism is enhanced by disorder because the renormalization of W^* by J is reduced by disorder. The asymmetry of disorder between electron-doped and hole-doped cuprate oxide superconductors must be, at least partly, responsible for that of antiferromagnetic phases between them. The so called Kumagai phase is characterized as an SDW state in a disordered system rather than a spin glass. The Neel temperature T_N about 300K of non-doped cuprate oxides can be explained by the reduction of T_N by critical thermal antiferromagnetic fluctuations in quasi-two dimensions.

27 pages, 10 figures (18 sub-figures). To be published in Journal of The Physical Society of Japan Vol.74 No.12 (2005)

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