NMR investigation of superconductivity and antiferromagnetism in CaFe$_2$As$_2$ under pressure

TL;DR

This study uses NMR to explore how pressure influences superconductivity and antiferromagnetism in CaFe$_2$As$_2$, revealing phase segregation and coexistence of magnetic order with superconductivity.

Contribution

First NMR investigation showing phase segregation and coexistence of superconductivity and antiferromagnetism in CaFe$_2$As$_2$ under pressure.

Findings

Phase segregation of PM and AFM phases over a pressure range.

AFM phase dominates at low temperatures.

Superconductivity coexists with magnetic order as detected by NMR.

Abstract

We report $^{75}$As NMR measurements in CaFe$_2$As$_2$, made under applied pressures up to 0.83 GPa produced by a standard clamp pressure cell. Our data reveal phase segregation of paramagnetic (PM) and antiferromagnetic (AFM) phases over a range of pressures, with the AFM phase more than 90 % dominant at low temperatures. In situ RF susceptibility measurements indicate the presence of superconductivity. $^{75}$As spin-lattice relaxation experiments indicate that the $^{75}$As nuclei sample the superconductivity while in the magnetically-ordered environment.