Emergence of Ferromagnetism from Planar Defects in EuSn2As2 Antiferromagnet

TL;DR

This study reveals that planar nano-defects in EuSn2As2 induce local ferromagnetic regions, explaining its complex magnetic behavior and providing insights into defect-driven magnetism in layered antiferromagnets.

Contribution

The paper demonstrates that planar defects in EuSn2As2 create local ferromagnetic phases, linking microstructural features to magnetic properties, a novel insight into defect-induced magnetism.

Findings

Planar defects form EuSnAs2 layers within EuSn2As2.

Defects promote local ferromagnetic ordering of Eu atoms.

Results explain nonlinear magnetization and hysteresis in the material.

Abstract

We report a study of nano-scale structural peculiarities of the antiferromagnetic layered semimetal EuSn2As2, and show that they are responsible for its puzzling magnetic properties. The high resolution transmission electron microscopy revealed the presence of planar defects in the lattice of the studied single crystals. Using a combination of microstructural and DFT analysis we demonstrated that a single planar nano-defects forms a layer of a distinct phase EuSnAs2, that is different from the EuSn2As2 phase of the bulk lattice. The smaller distance between Eu layers in the planar nano-defect promotes formation of local ferromagnetic (FM) ordering of the Eu atoms. On average, the planar defects form a weak ferromagnetic phase in the antiferromagnetic (AFM) host lattice. The obtained results explain several puzzling features in magnetic properties of A-type AFM materials: the nonlinear magnetization in low in-plane fields, ferromagnetic-type hysteresis in low field, and the upturn of the magnetic susceptibility in the AFM state at temperatures approaching zero.