Two-Dimensional Jeff=1/2 Antiferromagnetic Insulator Unraveled from Interlayer Exchange Coupling in Artificial Perovskite Iridate Superlattices

Abstract

We report an experimental investigation of the two-dimensional J eff = 1/2 antiferromagnetic Mott insulator by varying the interlayer exchange coupling in [(SrIrO3)1, (SrTiO3)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 SrTiO3 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 SrTiO3 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.

Novel spin-orbit coupling driven emergent states in iridate-based heterostructures

“…Application of epitaxial strain has been shown to allow controlled modulations to the material's properties [41,49,51,52,53,54]. Furthermore, layering of SrIrO 3 with band-insulating SrTiO 3 allows the creation of artificial analogues of the RP series iridates, with the advantage of enhanced strain control and the ability to synthesize structures not obtainable in bulk form [55,56]. Finally, replacing the band-insulating layer with active 3d magnetic oxides creates interfacial magnetic interactions which can capitalize on the strong SOC of the 5d state and introduce novel magnetic behavior [57, 58,59,60,61].…”

“…(c) In-plane remnant magnetization as function of temperature. Before measurement in zero-field, samples were cooled down under 5 kOe inplane magnetic field[56].…”

Spin-Orbit Semimetal SrIrO3 in the Two-Dimensional Limit

“…To study changes in electronic structure between the two end members of the RP series, previous studies have focused on varying the number of SrIrO 3 layers in [ðSrIrO 3 Þ m ; SrTiO 3 ] superlattices [13][14][15][16][17]. While these superlattices closely resemble the RP series, they are distinctly different from SrIrO 3 thin films since they are affected by interlayer coupling.…”

“…This was recently underlined by Hao et al by demonstrating that the interlayer coupling can be tuned through the number of SrTiO 3 u.c. [16]. By studying single ultrathin SrIrO 3 layers of different thicknesses, we directly address the effect of dimensionality and access the intrinsic properties of 2D SrIrO 3 , which forms a building block for spin-orbit coupled superlattices and heterostructures.…”

Interfacial charge-transfer Mott state in iridate–nickelate superlattices

“…SrIrO3 is an exotic semimetal due to its strong SOC (13,14). However, ICT does not occur in most artificial heterostructures and superlattices involving iridates studied to date, such as SrIrO3/SrTiO3 and SrIrO3/SrRuO3 systems (15)(16)(17)(18)(19)(20)(21)(22).…”