Strong pinning of vortices by antiferromagnetic domain boundaries in CeCo(In$_{1-x}$Cd$_x$)$_5$

TL;DR

This study investigates vortex pinning in CeCo(In$_{1-x}$Cd$_x$)$_5$, revealing that antiferromagnetic domain boundaries, rather than material defects, strongly pin vortices, especially evident through asymmetric peak effects at high fields.

Contribution

It demonstrates that vortex pinning in this compound is primarily due to antiferromagnetic domain boundaries, not crystallographic disorder, providing new insights into vortex behavior in magnetic superconductors.

Findings

Vortex pinning occurs at antiferromagnetic domain boundaries.

Asymmetric peak effect (ASPE) is linked to magnetic domain structures.

Pinning mechanism differs from conventional defect-based models.

Abstract

We have studied the isothermal magnetization $M(H)$ of CeCo(In$_{1-x}$Cd$_x$)$_5$ with $x$ = 0.0075 and 0.01 down to 50 mK. Pronounced field-history dependent phenomena occur in the coexistence regime of the superconducting and antiferromagnetic phases. At low-fields, a phenomenological model of magnetic-flux entry well explains $M(H)$ implying the dominance of bulk pinning effect. However, unless crystallographic quenched disorder is hysteretic, the asymmetric peak effect (ASPE) which appears at higher fields cannot be explained by the pinning of vortices due to material defects. Also the temperature dependence of the ASPE deviates from the conventional scenario for the peak effect. Comparison of our thermodynamic phase diagrams with those from previous neutron scattering and magnetoresistance experiments indicates that the pinning of vortices takes place at the field-history dependent antiferromagnetic domain boundaries.