Theory of the metamagnetic crossover in CeRu_2Si_2

TL;DR

This paper presents a theoretical model explaining the metamagnetic crossover in CeRu_2Si_2 through the competition of quantum spin fluctuations and exchange interactions, aligning well with experimental data.

Contribution

It introduces a model based on the periodic Anderson framework that captures the metamagnetic transition and the role of electron-lattice interactions in CeRu_2Si_2.

Findings

Reproduces experimental static quantities accurately.

Identifies the exchange interaction as key to the crossover.

Shows the sign change of exchange interaction with magnetization.

Abstract

Based on the periodic Anderson model, it is shown that the competition between the quenching of magnetic moments by local quantum spin fluctuations and a magnetic exchange interaction caused by the virtual exchange of pair excitations of quasiparticles in spin channels is responsible for the metamagnetic crossover in CeRu_2Si_2, cooperated with the electron-lattice interaction. The strength of the exchange interaction is proportional to the bandwidth of quasiparticles and its sign changes with increasing magnetizations; it is antiferromagnetic in the absence of magnetizations, whereas it is ferromagnetic in the metamagnetic crossover region. Experimental results of static quantities are well reproduced.