Induced-Moment Weak Antiferromagnetism and Orbital Order on the Itinerant-Localized Duality Model with Nested Fermi Surface: A Possible Origin of Exotic Magnetism in URu${}_{2}$Si$_{2}$

TL;DR

This paper proposes a duality model incorporating itinerant and localized electron features to explain weak antiferromagnetism and orbital order in URu2Si2, aligning with experimental observations of small magnetic moments and specific heat jumps.

Contribution

It introduces a duality model with an induced-moment mechanism and nesting properties to explain weak antiferromagnetism and orbital order in URu2Si2, providing a theoretical basis for experimental findings.

Findings

Small ordered magnetic moment explained by the model

Field dependence of magnetic moment matches recent experiments

Antiferromagnetic order induces tiny orbital order in f-electrons

Abstract

The weak antiferromagnetism of URu${}_{2}$Si${}_{2}$ is discussed on the basis of a duality model which takes into account salient features of both itinerant fermions and "localized" component of spin degrees of freedom. The problem is analyzed in the framework of induced-moment mechanism by taking a singlet-singlet crystal field scheme together with the nesting property of partial Fermi surface of itinerant fermions . It is shown that the extremely small ordered moment $m$ of ${\cal O}$($10^{-2}$$\times$$\mu_{B}$) can be compatible with the large specific-heat jump at the transition temperature $T_{N}$. Analysis performed in the presence of external magnetic field shows that the field dependence of $m$ in the limit T\to 0 and T_{N}$ do not scale except very near the critical field B which is consistent with a recent observation by Mentink. It is also shown that the antiferromagnetic magnetic order gives rise to a tiny amount of antiferromagnetic orbital order of f-electrons.