Towards universal magnetization curves in the superconducting state of RuSr2GdCu2O8

TL;DR

This study investigates the superconducting behavior of RuSr2GdCu2O8 using stationary SQUID magnetometry, suggesting that previous inconsistencies were due to measurement artifacts, and supports the presence of bulk superconductivity in this compound.

Contribution

The paper demonstrates that measurement artifacts caused by magnetic field inhomogeneities can explain previous inconsistent SQUID results, proposing a method to reveal universal superconducting behavior.

Findings

Stationary SQUID measurements show consistent superconducting behavior.

Field inhomogeneities affect SQUID magnetometry results.

Evidence supports bulk superconductivity in RuSr2GdCu2O8.

Abstract

Whereas resistivity and ac susceptibility measurements on the magnetic (Tm ~ 130 K) superconductor (Tc,onset ~ 50 K) RuSr2GdCu2O8 (Ru-1212Gd) reported by different research groups reveal a universal behavior in its superconducting state, this is not the case with the superconducting quantum interference device (SQUID) magnetization measurements. The reported SQUID measurements in the superconducting state of Ru-1212Gd reveal a variety of behaviors, leaving the question of bulk superconductivity for this compound open. We review several of the reported behaviors by presenting measurements done on our samples belonging to the same batch. Based on the observed sensitivity of Ru-1212Gd to magnetic field inhomogeneities when it is moved in the superconducting magnet of the SQUID magnetometer during the measurements, we suggest that the reported different behaviors can be the result of different field profiles in the superconducting magnet and not of different superconducting properties. In order to avoid the artifacts arising from moving the sample in an inhomogeneous field, we did measurements on a stationary Ru-1212Gd sample employing a home made SQUID magnetometer. The measured curves showed none of the suspicious ``symptoms'' present in the curves measured with a magnetometer employing sample movement (e.g. no reversal of the features observed in the superconducting state of Ru-1212Gd by a field reversal) and if verified by measurements on stationary samples by other groups a universal behavior in the superconducting state of Ru-1212Gd can be revealed by the SQUID measurements too. Our considerations support the existence of bulk superconductivity for Ru-1212Gd.