Dichotomy between in-plane magnetic susceptibility and resistivity anisotropies in extremely strained $BaFe_{2}As_{2}$

TL;DR

This study investigates the anisotropies in resistivity and magnetic susceptibility in strained BaFe₂As₂, revealing that resistivity anisotropy reflects magnetic properties more than nematicity, with anisotropy mainly below the magnetic transition temperature.

Contribution

The paper introduces a new method to measure in-plane anisotropies under large strain and demonstrates that resistivity anisotropy is more directly linked to magnetism than nematic order.

Findings

Resistivity anisotropy diverges similarly to elastoresistivity under strain.

Magnetic susceptibility anisotropy develops mainly below the magnetic transition temperature.

Anisotropy is influenced by spin-orbit coupling and intra-orbital contributions in the antiferromagnetic phase.

Abstract

The in-plane resistivity and uniform magnetic susceptibility anisotropies of $BaFe_{2}As_{2}$ are obtained with a new method, in which a large symmetry-breaking uniaxial strain is applied using a substrate with a very anisotropic thermal expansion. The resistivity anisotropy and its corresponding elastoresistivity exhibit very similar diverging behavior as those obtained from piezo-stack experiments. This suggests that the resistivity anisotropy is more a direct measure of magnetism than of nematicity, since the nematic transition is no longer well-defined under a large strain. In strong contrast to the large resistivity anisotropy above $T_{N}$, the anisotropy of the in-plane magnetic susceptibility develops largely below $T_{N}$. Using an itinerant model, we show that the observed anisotropy ($\chi_{b}>\chi_{a}$) is determined by spin-orbit coupling and the orientation of the magnetic moments in the antiferromagnetic phase, and that the anisotropy is dominated by intra-orbital ($yz,yz$) contributions of the Umklapp susceptibility.