Coexistence of superconductivity and ferromagnetism in the graphite-sulfur system

TL;DR

This paper reports the discovery of superconductivity coexisting with ferromagnetism in graphite-sulfur systems, characterized by anisotropic superconducting properties and a transition influenced by magnetic fields.

Contribution

It provides experimental evidence of coexistence of superconductivity and ferromagnetism in graphite-sulfur systems, including measurements of critical fields and penetration depth.

Findings

Superconductivity observed below 9.0 K in graphite-sulfur samples.

Superconductivity coexists with ferromagnetism with a Curie temperature above room temperature.

Transition between superconducting and ferromagnetic states can be controlled by magnetic field.

Abstract

Superconducting characteristics such as the Meissner-Ochsenfeld state, screening supercurrents and hysteresis loops of type-II superconductors were observed from the temperature and magnetic field dependences of the magnetic moment, m(T, H), in graphite powders reacted with sulfur for temperatures below 9.0 K. The temperature dependence of the lower critical field Hc1(T) was determined and the zero-temperature penetration depth, lambda(0), was estimated (lambda (0) = 227 nm). The superconductivity was observed to be highly anisotropic and to coexist with a ferromagnetic state that has a Curie temperature well above room temperature. A continuous transition from the superconducting state to the ferromagnetic state could be achieved by simply increasing the applied magnetic field.