Superconducting and ferromagnetic phases induced by lattice distortions in stoichiometric SrFe2As2 single crystals.

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 Tc=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 approximately 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.