Net Magnetization and Inhomogeneous Magnetic Order in a High-Tc Nickelate Superconductor

TL;DR

This study uncovers magnetic order and net magnetization in the high-Tc nickelate superconductor SECNO, revealing disordered, inhomogeneous magnetism that persists through the superconducting transition, distinct from other nickelates.

Contribution

It provides the first detailed characterization of magnetic order and net magnetization in SECNO using muon spin relaxation and neutron reflectometry, highlighting its unique magnetic properties.

Findings

Magnetic freezing occurs at higher temperatures than in other nickelates.

A substantial net magnetization of approximately 55 kA/m is observed.

Magnetism remains largely unchanged across the superconducting transition.

Abstract

High-temperature and high-magnetic-field-induced re-entrant superconductivity has been discovered in the infinite-layer nickelate $\mathrm{Sm_{1-x-y} Eu_x Ca_y Ni O_2}$ (SECNO). Infinite-layer nickelates are the closest known analogues of high-$\mathrm{T}_c$ cuprate superconductors, yet they host distinct magnetic ground states. Using low-energy muon spin relaxation and polarized neutron reflectometry, we reveal the magnetic order in SECNO. We find that magnetic freezing occurs at a higher-temperature than in other nickelate compounds, and that a substantial net magnetization of 55 $\,\mathrm{kA}\,\mathrm{m}^{-1}$ $\pm10 \,\mathrm{kA}\,\mathrm{m}^{-1}$ emerges and remains largely unchanged across the superconducting transition. The magnetism in SECNO is disordered and nonuniform.