Magnetism in artificial Ruddlesden-Popper iridates leveraged by structural distortions, interlayer coupling and ultra-fast optical excitation*

Many appealing structural and electronic analogies between iridates and traditional 3d-electron based cuprates have been identified. One crucial difference, however, is that iridates host spin-orbit coupled J_eff=1/2 magnetic moments rather than pure spin S = 1/2 moments. This coupling means that subtle structural modulations driven by heterostructuring in iridates can be leveraged to drive large changes in the magnetic interactions. This talk focuses on resonant x-ray scattering studies of this phenomenology in (SrIrO₃)_n-(SrTiO₃)_m and Sr₂IrO₄ based heterostructures. This includes a demonstration of how twisting of the Ir-O octahedra drive the magnetic interactions in n=1 and 2 (SrIrO₃)_n-(SrTiO₃)_m heterostructures and how these systems mimic the bulk Ruddelston-Popper iridates Sr_n+1Ir_nO_3n+1 [1]. It will further cover how the magnetic state of SrIrO₃ changes as a function of the number of intervening SrTiO₃ layers m [2]. It was found that both interlayer coupling and local anisotropy act in concert to stabilize Mott insulating antiferromagnetic states and that the relative importance of these effects change with m. An emergent new field focuses on further modifying magnetic interactions with ultra-fast laser excitation. It has recently been shown that x-ray free electron lasers can be used to probe the nature of the magnetic correlations in transient states of iridates and that the magnetic dynamics is strongly dependent on the dimensionality of the magnetic interactions [3].

1. D. Meyers et al., arXiv:1707.08910 (2017)

2. L. Hao et al., Phys. Rev. Lett. 119, 027204 (2017)

3. M. P. M. Dean et al., Nature Materials, 15 601-605 (2016)