Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session V25: Spin-Orbit, Interface, and Domain Wall Physics in Magnetic IridatesInvited
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Sponsoring Units: GMAG DMP Chair: Brian Kirby, NIST -Natl Inst of Stds & Tech Room: LACC 403B |
Thursday, March 8, 2018 2:30PM - 3:06PM |
V25.00001: Emergent Magnetic Phenomena in Iridate-Based Superlattices Invited Speaker: Di Yi Heterointerfaces of complex oxides provide a rich playground to explore emergent phenomena that are not found in the bulk and have been largely studied in 3d transition metal oxide (TMO) heterostructures. With recent advances in the synthesis of 5d TMOs, heterostructures based on 3d and 5d TMOs offer new model systems to realize emergent functionalities of complex oxides. In this talk, we demonstrate emergent magnetism and perpendicular magnetic anisotropy in iridate-based superlattices. We focus on superlattices comprised of the colossal magnetoresistive La1-xSrxMnO3 (LSMO) and the paramagnetic SrIrO3. Weak ferromagnetism and a new spin-orbit state are induced in SrIrO3 due to dimensional confinement and interfacial coupling. On the other hand, LSMO shows ferromagnetism in superlattices for all compositions of x (x=0, 0.3, 0.5, 0.8, 1.0). The stabilization of ferromagnetism in both La rich and Sr rich superlattices points to an interfacial charge transfer which is confirmed by x-ray absorption spectroscopy measurements. Surprisingly, we find a strong interface-induced perpendicular magnetic anisotropy (PMA) for Sr rich compositions. The PMA changes as a function of x. Synchrotron x-ray diffraction and linear dichroism measurements indicate a strong correlation between the PMA and the oxygen octahedral rotations at interfaces. Our comprehensive study provides insights into unique emergent phenomena driven by the 3d-5d heterointerfaces due to the delicate interplay of charge, spin, orbital and lattice degrees of freedom. The emergence of a strong PMA also points to the potential of its incorporation in future spintronic applications. |
Thursday, March 8, 2018 3:06PM - 3:42PM |
V25.00002: Magnetism in artificial Ruddlesden-Popper iridates leveraged by structural distortions, interlayer coupling and ultra-fast optical excitation Invited Speaker: Mark Dean 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 Jeff=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 Srn+1IrnO3n+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]. |
Thursday, March 8, 2018 3:42PM - 4:18PM |
V25.00003: Investigating Interfacial Spin Orbit Physics with Density Functional Theory Invited Speaker: Satoshi Okamoto Relativistic spin-orbit coupling (SOC) is one of the important ingredients to generate novel phenomena in a solid, such as topological insulators. In complex oxides, the SOC and Coulomb repulsive interactions coexist. In order to understand or predict useful functionalities of complex oxides, it is crucial to consider the competition or cooperation between these effects in a realistic manner. In this talk, I will present our theoretical work on complex oxides based on density functional theory type calculations mainly focusing on iridium-based oxides. Considering iridium oxide heterostructures, I will first discuss possible topological insulating states [1] and unusual charge transfer effects [2]. For the latter, the detailed comparison with recent experimental results [3] will be presented. I will then discuss the electronic structure of a bulk iridium oxide and related compounds, which appear to have unmixed Jeff=1/2 states [4]. |
Thursday, March 8, 2018 4:18PM - 4:54PM |
V25.00004: Metallicity and Topology in Iridate Domain Walls Invited Speaker: Youhei Yamaji Cooperation and competition between strong electron correlations and spin-orbit couplings have attracted much attention. Iridium oxides offer playgrounds for such an interplay and indeed exhibit intriguing phenomena. Especially, theoretical predictions on realization of topological Weyl semimetals had inspired extensive studies of pyrochlore iridates R2Ir2O7 (R: rare-earth elements). However, direct observation of Weyl electrons has hardly been realized in R2Ir2O7, yet. |
Thursday, March 8, 2018 4:54PM - 5:30PM |
V25.00005: Spin orbit coupled 3d–5d quantum oxide heterostructures Invited Speaker: Ho Nyung Lee The controlled synthesis of quantum oxide heterostructures provides tremendous opportunities in producing materials with remarkable physical properties and functionalities. We have successfully synthesized superlattices and heterostructures composed of 3d and 5d transition metal oxides (TMOs). These material systems are an ideal test bed to take advantage of the strong correlation in 3d TMOs and the spin orbit coupling in heavy-element 5d TMOs. To manipulate the Dzyaloshinskii-Moriya interaction in 3d-5d heterostructures, we engineered the interfaces between 3d and 5d TMOs, in such way to break the inversion symmetry. We will present our observations on exotic quantum phenomena, including charge transfer induced interfacial magnetism and topologically non-trivial spin textures, that are not present in the constituent materials. |
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