Dual Nature of Fe1−δAs Nanoparticles: High- T C Superconductivity Amidst Magnetic Ordering

Abstract

Exploring the interplay between magnetism and superconductivity is key to understanding unconventional superconductivity. Here, we report the coexistence of superconductivity and magnetism in Fe1−δAs nanoparticles synthesized via a polyol-based method. Structural analysis confirms a predominant FeAs phase (∼98%) with a minor Fe3O4 secondary phase (∼2%), while magnetization measurements reveal a superconducting transition at ∼35 K. Isothermal M(H) loops at 2 and 10 K exhibit a superimposed superconducting and ferromagnetic-like hysteresis, indicating a complex competition between these states. Temperature-dependent resistivity further supports this coexistence, showing a superconducting transition with distinct electronic transport behavior. The anomalous magnetic response and high TC suggest an unconventional superconducting mechanism, possibly mediated by spin fluctuations or local inhomogeneities. These findings provide critical insights into the correlation between superconductivity and magnetism in Fe-based systems, highlighting the role of microstructural effects in stabilizing competing electronic phases and paving the way for further exploration of unconventional superconducting states.