Effects of proton irradiation on the magnetic superconductor EuFe2(As1 − xPx)2

We report on the effects of 3.5 MeV proton irradiation on single crystals of the magnetic superconductor EuFe2(As1 − xPx)2, investigated at microwave frequencies by a coplanar waveguide resonator technique. We studied the relative strength of the two collective phenomena by analyzing the dependence of their onset temperatures on different perturbations: magnetic fields and structural disorder. Results suggest that superconductivity and magnetism in this material are two competing orders: as the former is suppressed by irradiation or by excess P doping, the latter reinforces and manifests itself at higher temperatures. The ability to modulate superconductivity and magnetism in EuFe2(As1 − xPx)2 by disorder and in-plane magnetic field, respectively, offers the chance to tailor, even on a local scale, their relative weights. This could be useful for the aim of engineering this material for specific applications.