Metamagnetic phase transition in ferromagnetic superconductor URhGe

TL;DR

This paper investigates the metamagnetic phase transition in the ferromagnetic superconductor URhGe, explaining the phenomena through magnetic anisotropy, and discusses the reentrant superconductivity near the transition point.

Contribution

It provides a theoretical model for the metamagnetic transition in URhGe based on magnetic anisotropy and describes the reentrant superconductivity near the critical point.

Findings

Metamagnetic transition line ends at a critical point.

Reentrant superconductivity occurs near the transition due to increased magnetic susceptibility.

Behavior of upper critical field is linked to magnetic susceptibility in related compounds.

Abstract

Ferromagnetic superconductor URhGe has orthorhombic structure and possesses spontaneous magnetisation along the c-axis. Magnetic field directed along the $b$-axis suppresses ferromagnetism in $c$-direction and leads to a metamagnetic transition into polarised paramagnetic state in the $b$-direction. The theory of these phenomena based on the specific magnetic anisotropy of this material in $(b,c)$ plane is given. Line of the first order metamagnetic transition ends at a critical point. The Van der Waals - type description of behaviour of physical properties near this point is developed. The triplet superconducting state destroyed by orbital effect is recreated in vicinity of the transition. It is shown that the reentrance of superconductivity is caused by the sharp increase of magnetic susceptibility in $b$ direction near the metamagnetic transition. The specific behaviour of the upper critical field in direction of spontaneous magnetisation in UCoGe and in UGe$_2$ related to the field dependence of magnetic susceptibility is discussed.