Superconducting and ferromagnetic phases induced by lattice distortions in SrFe2As2

TL;DR

This study demonstrates that lattice distortions, caused by internal strain and defects, induce superconducting and ferromagnetic phases in SrFe2As2 crystals, highlighting the role of structural imperfections in emergent quantum states.

Contribution

It reveals that internal crystallographic strain from planar defects promotes superconductivity and ferromagnetism in SrFe2As2 at ambient pressure, a novel insight into strain-induced quantum phenomena.

Findings

Superconductivity appears below T_c = 21 K with full resistivity transition.

Superconducting phase can be reversibly destroyed and reinstated by heat and mechanical treatment.

Ferromagnetic moment correlates with the superconducting volume fraction.

Abstract

Single crystals of SrFe2As2 grown using a self-flux solution method were characterized via x-ray, transport and magnetization studies, revealing a superconducting phase below T_c = 21 K characterized by a full electrical resistivity transition and partial diamagnetic screening. The reversible destruction and reinstatement of this phase by heat treatment and mechanical deformation studies, along with single-crystal X-ray diffraction measurements, indicate that internal crystallographic strain originating from c-axis-oriented planar defects plays a central role in promoting the appearance of superconductivity under ambient pressure conditions in ~90% of as-grown crystals. The appearance of a ferromagnetic moment with magnitude proportional to the tunable superconducting volume fraction suggests that these phenomena are both stabilized by lattice distortion.