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

TL;DR

This study investigates the in-plane electrical resistivity anisotropy in detwinned SrFe2As2 crystals, revealing how strain influences anisotropy development and suggesting nematicity is absent in strongly first-order transition compounds.

Contribution

It provides the first detailed analysis of resistivity anisotropy in SrFe2As2, demonstrating the effects of strain and confirming the first-order nature of its structural transition.

Findings

Resistivity is lower along the orthorhombic a_o direction.

Resistivity anisotropy develops with increased strain above T_{TO}.

Structural transition remains unaffected by moderate strain.

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, $T_{\textrm{TO}}$. 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 $T_{\textrm{TO}}$. With the increase of strain, the resistivity anisotropy starts to develop above $T_{\textrm{TO}}$, 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.