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arXiv · 1703.04645

Two-dimensional ${J}_{\rm eff}$ = 1/2 antiferromagnetic insulator unraveled from interlayer exchange coupling in artificial perovskite iridate superlattices

L. Hao·D. Meyers·C. Frederick·G. Fabbris·J. Y. Yang·N. Traynor·L. Horak·D. Kriegner·Y. S. Choi·J. W. Kim·D. Haskel·P. J. Ryan·M. P. M. Dean·J. Liu
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Abstract

We report an experimental investigation of the two-dimensional ${J}_{\rm eff}$ = 1/2 antiferromagnetic Mott insulator by varying the interlayer exchange coupling in [(SrIrO$_3$)$_1$, (SrTiO$_3$)$_m$] ($m$ = 1, 2 and 3) superlattices. Although all samples exhibited an insulating ground state with long-range magnetic order, temperature-dependent resistivity measurements showed a stronger insulating behavior in the $m$ = 2 and $m$ = 3 samples than the $m$ = 1 sample which displayed a clear kink at the magnetic transition. This difference indicates that the blocking effect of the excessive SrTiO$_3$ layer enhances the effective electron-electron correlation and strengthens the Mott phase. The significant reduction of the Neel temperature from 150 K for $m$ = 1 to 40 K for $m$ = 2 demonstrates that the long-range order stability in the former is boosted by a substantial interlayer exchange coupling. Resonant x-ray magnetic scattering revealed that the interlayer exchange coupling has a switchable sign, depending on the SrTiO$_3$ layer number $m$, for maintaining canting-induced weak ferromagnetism. The nearly unaltered transition temperature between the $m$ = 2 and the $m$ = 3 demonstrated that we have realized a two-dimensional antiferromagnet at finite temperatures with diminishing interlayer exchange coupling.

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L. Hao, D. Meyers, C. Frederick, G. Fabbris, J. Y. Yang, N. Traynor, L. Horak, D. Kriegner, Y. S. Choi, J. W. Kim, D. Haskel, P. J. Ryan, M. P. M. Dean, J. Liu. 2017-03-14. Two-dimensional ${J}_{\rm eff}$ = 1/2 antiferromagnetic insulator unraveled from interlayer exchange coupling in artificial perovskite iridate superlattices. https://doi.org/10.1103/physrevlett.119.027204

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