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

Abstract

Intrinsic, in-plane anisotropy of electrical resistivity was studied on mechanically detwinned single crystals of SrFe${}_2$As${}_2$ above and below the temperature of the coupled structural/magnetic transition, $T_{\mathrm{TO}}$. 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 CaFe${}_2$As${}_2$ and BaFe${}_2$As${}_2$ compounds. A strongly first-order structural transition in SrFe${}_2$As${}_2$ 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 $T_{\mathrm{TO}}$. With the increase of strain, the resistivity anisotropy starts to develop above $T_{\mathrm{TO}}$, 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. DOI: http://dx.doi.org/10.1103/PhysRevB.83.134505 ©2011 American Physical Society