In-plane anisotropy of electrical resistivity in strain-detwinned SrFe2As2

Intrinsic, in-plane anisotropy of electrical resistivity was studied on mechanically detwinned single crystals of SrFe2As2 above and below the temperature of the coupled structural/magnetic transition, T-TO. Resistivity is smaller for electrical current flow along the orthorhombic a(o) direction (direction of antiferromagnetically alternating magnetic moments) and is larger for transport along the b(o) direction (direction of ferromagnetic chains), which is similar to CaFe2As2 and BaFe2As2 compounds. A strongly first-order structural transition in SrFe2As2 was confirmed by high-energy x-ray measurements, with the transition temperature and character unaffected by moderate strain. For small strain levels, which are just sufficient to detwin the sample, we find a negligible effect on the resistivity above TTO. With the increase of strain, the resistivity anisotropy starts to develop above TTO, clearly showing the relation of anisotropy to an anomalously strong response to strain. Our study suggests that electronic nematicity cannot be observed in the FeAs-based compounds in which the structural transition is strongly first order