Persistent detwinning of iron pnictides by small magnetic fields

TL;DR

This study demonstrates that small magnetic fields can induce persistent detwinning in EuFe$_2$As$_2$, enabling the investigation of intrinsic electronic anisotropy without external symmetry-breaking forces.

Contribution

It reveals a new mechanism of persistent detwinning in iron pnictides via Eu$^{2+}$ magneto-elastic coupling, significantly reducing the required magnetic field compared to other compounds.

Findings

0.1T magnetic field induces persistent detwinning below 19K

Detwinning remains stable up to 190K without external force

Eu$^{2+}$ ions enable low-field, persistent detwinning

Abstract

Our comprehensive study on EuFe$_2$As$_2$ reveals a dramatic reduction of magnetic detwinning fields compared to other AFe$_2$As$_2$ (A = Ba, Sr, Ca) iron pnictides by indirect magneto-elastic coupling of the Eu$^{2+}$ ions. We find that only 0.1T are sufficient for persistent detwinning below the local Eu$^{2+}$ ordering; above $T_\text{Eu}$ = 19K, higher fields are necessary. Even after the field is switched off, a significant imbalance of twin domains remains constant up to the structural and electronic phase transition (190K). This persistent detwinning provides the unique possibility to study the low temperature electronic in-plane anisotropy of iron pnictides without applying any symmetrybreaking external force.