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.
@article{arxiv.1804.08780,
title = {Giant magnetic response of a two-dimensional antiferromagnet},
author = {Lin Hao and D. Meyers and Hidemaro Suwa and Junyi Yang and Clayton Frederick and Tamene R. Dasa and Gilberto Fabbris and Lukas Horak and Dominik Kriegner and Yongseong Choi and Jong-Woo Kim and Daniel Haskel and Philip J. Ryan and Haixuan Xu and Cristian D. Batista and M. P. M. Dean and Jian Liu},
journal= {arXiv preprint arXiv:1804.08780},
year = {2018}
}