Itinerant to Localized Transition and Metamagnetism in the Kondo Lattice

概要

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We investigate the characteristics of itinerant to localized transition of $ f$ electrons in heavy fermion systems in terms of the generalized Ginzburg–Landau (GL) theory based on the Kondo lattice model, in which the static thermal fluctuations of Kondo bosons are taken into account by the mean mode–mode coupling approximation. For a finite gradient term in the GL expansion corresponding with heavy fermions, we obtain a first-order phase transition from the mean-field heavy-fermion state at low temperatures ($T$) and low magnetic fields ($H$) to the asymptotically free local moment regime at high $T$ and high $H$. The asymptotic freedom of the local moments at high $T$ is represented by a gradual logarithmic function of $\ln T$ similarly to the impurity Kondo problem, whereas that at high $H$ by a relatively sharp function of $H^{-1}$ different from $\ln H$, giving rise to a metamagnetism similar to the experimental results of heavy fermion materials.
2009-04-15