Size of stripe domains in a superconducting ferromagnet

TL;DR

This paper investigates how superconductivity influences stripe domain structures in superconducting ferromagnets, revealing domain shrinkage effects, stability conditions, and differences between singlet and triplet pairing, with implications for experimental materials.

Contribution

It provides a theoretical analysis of superconducting screening effects on domain structures, including stability criteria and the impact of pairing symmetry in ferromagnetic superconductors.

Findings

Superconductivity causes domain shrinkage.

A critical penetration depth determines domain stability.

Differences between singlet and triplet superconductivity effects.

Abstract

In a superconducting ferromagnet, the superconducting state appears in the ferromagnetic phase where usually a domain structure has already developed. We study the influence of the superconducting screening currents on a stripe structure with out-of-plane magnetization, in a film of arbitrary thickness. We find that superconductivity always induces a shrinkage of the domains, and there is a critical value of penetration depth below which a mono-domain structure is more stable than the periodic one. Furthermore we investigate the possible different effects of singlet and triplet superconductivity on the domain width, as well as the conditions for the existence of vortices in the domains. The obtained results are then discussed in light of the experimental data of superconducting ferromagnets URhGe, UGe2, and UCoGe.