Inverse magnetic proximity effects in superconducting In-Ni and Sn-Ni nanoparticle assemblies

Abstract

We report on experimental evidence of non-s-wave pairing in In and Sn nanoparticle assemblies. The superconducting transition temperature TC of the In and Sn nanoparticles varies noticeably with the particle diameter. Surprisingly, TC shifts to a noticeably higher temperature when magnetic Ni nanoparticles are introduced into the vicinity of the superconducting nanoparticles. The TC increases further when the magnetic Ni nanoparticles are brought even closer to the superconducting nanoparticles. There is a critical Ni composition and a critical spatial separation between the magnetic and superconducting nanoparticles that must be reached before their magnetic proximity will suppress the superconductivity. A qualitative mechanism is proposed to understand the present observations.