Giant magnetic response of a two-dimensional antiferromagnetic iridate*

Layered iridates are featured of preserving a hidden SU(2) symmetry such that anisotropic exchange interactions have no contribution to spin anisotropy. Achieving this symmetry, however, is highly challenging because it's necessary to incorporate strong spin-orbit coupling, control the 2D lattice structure, and minimize the interlayer coupling. We solved this issue through top-down design and bottom-up synthesis of SrIrO₃ and SrTiO₃ superlattices [1] to realize a pseudospin-half antiferromagnetic (AFM) square lattice. We observed giant AFM responses to sub-tesla external fields by exploiting the strong 2D critical fluctuations preserved under the symmetry-invariant exchange anisotropy. The observed field-induced logarithmic increase of the ordering demonstrates a new pathway for the highly efficient control of AFM order [2]. Further investigation on the transport properties suggests a novel coupling between AFM fluctuations and charge fluctuations, highlights the application potential in semiconductor devices.
[1] L. Hao, et.al. Phys. Rev. Lett. 119, 027204 (2017).
[2] L. Hao, et.al. Nat. Phys. 14, 806–810 (2018).