Giant magnetic response of a two-dimensional antiferromagnet

TL;DR

This paper reveals a giant magnetic response in a two-dimensional antiferromagnet, achieved through a novel symmetry-invariant approach exploiting spin-orbit coupling, enabling efficient control of antiferromagnetic order with small external fields.

Contribution

The study introduces a new method to induce large magnetic responses in 2D antiferromagnets using symmetry-invariant exchange anisotropy and spin-orbit coupling, overcoming previous limitations.

Findings

Giant AFM responses to sub-Tesla fields observed.

Logarithmic increase of the ordering temperature under external fields.

Artificial superlattice enables symmetry-invariant control of AFM order.

Abstract

A fundamental difference between antiferromagnets and ferromagnets is the lack of linear coupling to a uniform magnetic field due to the staggered order parameter. Such coupling is possible via the Dzyaloshinskii-Moriya (DM) interaction but at the expense of reduced antiferromagnetic (AFM) susceptibility due to the canting-induced spin anisotropy. We solve this long-standing problem with a top-down approach that utilizes spin-orbit coupling in the presence of a hidden SU(2) symmetry. We demonstrate giant AFM responses to sub-Tesla external fields by exploiting the extremely strong two-dimensional critical fluctuations preserved under a symmetry-invariant exchange anisotropy, which is built into a square-lattice artificially synthesized as a superlattice of SrIrO3 and SrTiO3. The observed field-induced logarithmic increase of the ordering temperature enables highly efficient control of the AFM order. As antiferromagnets promise to afford switching speed and storage security far beyond ferromagnets, our symmetry-invariant approach unleashes the great potential of functional antiferromagnets.