Stoner gap in the superconducting ferromagnet UGe2

TL;DR

This study investigates the ferromagnetic and superconducting properties of UGe2 under pressure, demonstrating that its magnetic behavior aligns with a Stoner model and exploring the interplay between ferromagnetism and superconductivity.

Contribution

The paper provides a detailed analysis of UGe2's magnetic state under pressure using the Stoner model, linking ferromagnetism and superconductivity.

Findings

Stoner gap decreases with pressure

Magnetization behavior explained by a conventional Stoner model

Ferromagnetic state is a fully polarized heavy quasiparticle state

Abstract

We report the temperature ($T$) dependence of ferromagnetic Bragg peak intensities and dc magnetization of the superconducting ferromagnet UGe2 under pressure ($P$). We have found that the low-$T$ behavior of the uniform magnetization can be explained by a conventional Stoner model. A functional analysis of the data produces the following results: The ferromagnetic state below a critical pressure can be understood as the perfectly polarized state, in which heavy quasiparticles occupy only majority spin bands. A Stoner gap $\Delta(P)$ decreases monotonically with increasing pressure and increases linearly with magnetic field. We show that the present analysis based on the Stoner model is justified by a consistency check, i.e., comparison of density of states at the Fermi energy deduced from the analysis with observed electronic specific heat coeffieients. We also argue the influence of the ferromagnetism on the superconductivity.