Theory of the metamagnetic crossover in CeRu_2Si_2
Abstract
The metamagnetic crossover in CeRu_2Si_2 is investigated by the 1/d expansion method, with d being the spatial dimensionality. The competition between the quenching of magnetic moments by local quantum spin fluctuations and Weiss's magnetic mean fields, both of which are leading order in 1/d, is responsible for the metamagnetic crossover. Ferromagnetic spin fluctuations or paramagnons, which are of higher order in 1/d, are significant only in the regionof the metamagnetic crossover. A treatment of a previous paper [Phys. Rev. B 57, 5891 (1998)] is improved; when a pseudogap in the density of quasiparticle states, which is characteristic of 4f systems, is large enough,the double-peak structure in the specific heat curves is reproduced as well as the magnetization process.Keywords
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