Direct visualization and control of antiferromagnetic domains and spin reorientation in a parent cuprate

TL;DR

This study uses magnetic optical SHG to visualize and control antiferromagnetic domains in a parent cuprate, revealing temperature-dependent domain behavior and a spin reorientation transition that enables deterministic AFM state switching.

Contribution

It introduces a direct optical method to visualize and manipulate AFM domains in a cuprate, uncovering a temperature-driven spin reorientation transition and domain control mechanisms.

Findings

Visualization of AFM domains via SHG imaging.

Observation of a spin reorientation transition at ~97 K.

Deterministic switching of AFM states using thermal or laser heating.

Abstract

We report magnetic optical second-harmonic generation (SHG) polarimetry and imaging on Sr$_2$Cu$_3$O$_4$Cl$_2$, which allows direct visualization of the mesoscopic antiferromagnetic (AFM) structure of a parent cuprate. Temperature- and magnetic-field-dependent SHG reveals large domains with 90$^{\circ}$ relative orientations that are stabilized by a combination of uniaxial magnetic anisotropy and the Earth's magnetic field. Below a temperature $T_R$ $\sim$ 97 K, we observe an unusual 90$^{\circ}$ spin reorientation transition, possibly driven by competing magnetic anisotropies of the two copper sublattices, which swaps the AFM domain states while preserving the domain structure. This allows deterministic switching of the AFM states by thermal or laser heating. Near $T_R$, the domain walls become exceptionally responsive to an applied magnetic field, with the Earth's field sufficient to completely expel them from the crystal. Our findings unlock opportunities to study the mesoscopic AFM behavior of parent cuprates and explore their potential for AFM technologies.