Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session C23: Controlling Magnetism in Oxide Heterostructures IIFocus
|
Hide Abstracts |
Sponsoring Units: GMAG DMP DCOMP Chair: Yaohua Liu, Oak Ridge National Lab Room: LACC 402B |
Monday, March 5, 2018 2:30PM - 2:42PM |
C23.00001: Controlling the magnetism of the Mott insulator LaTiO3 by interface engineering Zaher Salman, David Cortie, Daniel McNally, Zhiming Wang, W MacFarlane, Elvezio Morenzoni, Thomas Prokscha, Thorsten Schmitt, Andreas Suter, milan radovic, Robert Kiefl We present an investigation of the magnetic, electronic and structural properties of thin films of the Mott insulator LaTiO3 (LTO) grown on insulating SrTiO3 (STO) and LaAlO3 (LAO) substrates. As in the case of LAO/STO interface, high mobility 2DEG and superconductivity have been reported at LTO/STO interfaces, while the LTO/LAO interfaces remain insulating. Using depth resolved low energy muon spin relaxation (LE-μSR) and β-detected NMR (β-NMR) we find that while LTO undergoes antiferromagnetic ordering on LAO it becomes non-magnetic when grown on STO. The observed magnetic transition temperature in the film, ~75 K, is significantly suppressed compared to bulk LTO (~140 K). Surprisingly, we detect a clear interface proximity effect to the LTO/STO interface, where the magnetism becomes gradually stronger as we probe further away from the interface. The effect is attributed to charge transfer effects at the LTO/STO interface. The results demonstrate the potential of tunability of the magnetic and electronic properties of a Mott insulator by interface engineering. |
Monday, March 5, 2018 2:42PM - 2:54PM |
C23.00002: Anomalous Hall effect in high mobility La doped EuTiO3 films on LSAT substrates grown by gas source molecular beam epitaxy Kei Takahashi, Hiroaki Ishizuka, Tomoki Murata, Qing Wang, Yoshinori Tokura, Naoto Nagaosa, Masashi Kawasaki A magnetic semiconductor EuTiO3 is one of the ideal systems to control the anomalous Hall effect (AHE) by tuning the Fermi level through the Berry curvatures. In our previous work, we demonstrated the sign of AHE was reversed by shifting the Fermi level for La doped EuTiO3 (Eu1-xLaxTiO3) films on LSAT substrates grown by pulsed laser deposition (PLD). However, the observed AHE for the PLD films did not fully reflect the fine structures of band crossing due to the short scattering life time. |
Monday, March 5, 2018 2:54PM - 3:06PM |
C23.00003: Fabrication and magnetotransport properties of high mobility EuTiO3 quantum wells Kazuki Maruhashi, Kei Takahashi, Yoshinori Tokura, Masashi Kawasaki EuTiO3 (ETO) is a magnetic semiconductor with an antiferromagnetically ordering at 5.5 K for the 4f7 moments on Eu2+ site. Electron carriers can be doped into Ti t2g conduction band by substituting Eu2+ by La3+. We previously reported a peculiar behavior of anomalous Hall effect (AHE) of compressively strained La doped EuTiO3 (Eu1-xLaxTiO3) films on LSAT substrates grown by pulsed laser deposition (PLD). |
Monday, March 5, 2018 3:06PM - 3:42PM |
C23.00004: Carrier Density Control of Magnetism and Hall Effects in EuTiO3 Films Invited Speaker: Susanne Stemmer The topological Hall effect is a hallmark of topologically nontrivial (chiral) spin textures and can be observed as a distinct, additional contribution in Hall measurements that is superposed on the ordinary and anomalous Hall effects. Oxide films and interfaces that support topologically nontrivial spin textures are interesting, because the potential for control by electric field effect and because proximity effects can be utilized to realize other exotic states within all-epitaxial heterostructures. In this talk, we discuss the role of carrier density and band structure in the topological and anomalous Hall effects in thin films of Eu1-xSmxTiO3 grown by molecular beam epitaxy. The carrier density controls the sign and strength of the topological and anomalous Hall effects, the spin textures, and other effects, such as metamagnetic transitions. We will discuss the results in terms of the interactions between electronic and spin structures in this material. |
Monday, March 5, 2018 3:42PM - 3:54PM |
C23.00005: Spin-to-charge conversion through Rashba coupling in SrTiO3-based two-dimensional electron gases Diogo Vaz, Paul Noël, Edouard Lesne, Eric Jacquet, Gyanendra Singh, Nicolas Bergeal, Jean-Philippe Attané, Matthieu Jamet, Laurent Vila, Agnes Barthelemy, Manuel Bibes The quasi 2D electron system (q2DES) that forms at the interface between LaAlO3 (LAO) and SrTiO3 (STO) has attracted much attention from the oxide electronics community. Among its many low dimensional physical effects, the strong Rashba spin-orbit coupling present at the interface could be exploited for spin-to-charge interconversion, which presents advantages for the future of spintronics. We will present experiments performed on the q2DES formed at NiFe/LAO/STO and NiFe/(metal)/STO heterostructures. We investigating the nature of the inverse Edelstein effect (responsible for the spin-to-charge conversion) through a combination of spin pumping, magnetotransport, spectroscopy and gating experiments. We found a highly efficient spin-to-charge conversion which is tunable by a gate voltage. Results were then interpreted in terms of a crossover between the occupancy of one to several bands with different orbital characters and different spin-orbit textures. |
Monday, March 5, 2018 3:54PM - 4:06PM |
C23.00006: Describing paramagnetic phases of ABO3 transition metal oxide perovskites with Density Functional Theory Julien Varignon, Manuel Bibes, Alex Zunger ABO3 oxide perovskites, where B is a transition metal element with partly occupied 3d shells often show in their spin disordered paramagnetic (PM) phases insulating behavior, whereas naïve band theory systematically predicts metallic state. The latter qualitative failure had motivated explicitly correlated theoretical approaches going beyond single determinant DFT approaches.We enquire what is the minimum theoretical description that correctly captures gapped PM phases for open shell systems. Whereas naïve band theory was previously applied to PM phases by assuming zero moment on an atom-by-atom basis (producing incorrectly a non magnetic metal), we permit more flexible unit cells by using the “special quasi-random structure” methodology (where the total moment is zero but local disordered configurations can have moments), and allow energy-lowering symmetry breaking by way of correctly occupying partially filled degenerate levels. We find that DFT can reproduce band gaps of spin-disordered phases for several Mott insulating ABO3 oxides with different B atom d fillings. |
Monday, March 5, 2018 4:06PM - 4:18PM |
C23.00007: A living-dead magnetic layer in ferrimagnetic DyTiO3 thin films and how to revive it Raphael Aeschlimann, Daniele Preziosi, Julien Varignon, Cinthia Piamonteze, Florin Radu, Sergio Valencia, Jacobo Santamaria, A. Barthélémy, Manuel Bibes When ferromagnetic films become ultrathin, key properties such as the Curie temperature and the saturation magnetization are usually depressed. This effect has been thoroughly investigated in half-metallic manganites, but much less in ferrimagnetic insulating perovskites such as rare-earth titanates RTiO3, despite the appeal of these materials to design correlated two-dimensional electron gases. Here, we report on the magnetic properties of epitaxial DyTiO3 thin films. Above 50 nm the films show a bulk-like response, but surprisingly their saturation magnetization strongly increases at low thickness. We model this behavior using a classical model of “dead layer” but we assume that this layer is actually “living”, i.e. it responds to the magnetic field through a strong paramagnetic susceptibility. Through depth-dependent X-ray spectroscopy, we show that the “living-dead layer” corresponds to surface regions where magnetic (S=1/2) Ti3+ become non-magnetic Ti4+ ions, leaving Dy3+ ions magnetically uncoupled and thus unleashing their paramagnetic response. Accordingly, we find that capping the film with an epitaxial LaAlO3 layer preserves the Ti3+ state and restores the pristine ferrimagnetic behavior. |
Monday, March 5, 2018 4:18PM - 4:54PM |
C23.00008: GMAG Student Dissertation Award: When conductivity and magnetism emerge at a spinel/perovskite heterointerface Invited Speaker: Dennis Christensen The plethora of fascinating properties observed in oxide heterostructures has attracted a lot of interest. Most noticeably, the confined electron gas formed at the interface between the two insulators LaAlO3 and SrTiO3 features e.g. gate-tunable superconductivity, ferromagnetism and non-volatile memory effects. Numerous studies have been devoted to understand the origin of the conductivity along with enhancing its properties, in particular the electron mobility. Recently, we found1 that substituting perovskite LaAlO3 with spinel γ-Al2O3 can produce a confined electron gas with a record-high electron mobility exceeding 140,000 cm2/Vs. Here, we show that the γ-Al2O3/SrTiO3 interface conductivity originates from oxygen vacancies and use defect engineering to control various interface properties2. In addition, we reproduce the high mobility and show that it coexists with a strain-tunable magnetic order below 40 K and a positive, non-saturating magnetoresistance of up to 80,000% at 15 T. The study evidences that the γ-Al2O3/SrTiO3 heterostructure paves the way for combining lattice, spin and electronic degrees of freedom. |
Monday, March 5, 2018 4:54PM - 5:06PM |
C23.00009: Gate-tunable THz emission at oxide interfaces via ultrafast spin-to-charge current conversion Qi Zhang, Deshun Hong, Changjiang Liu, Richard Schaller, Dillon Fong, Anand Bhattacharya, Haidan Wen Two-dimensional electron systems at oxide interfaces such as LaAlO3 / SrTiO3 provide promising platforms for achieving fast, tunable, and efficient spin-charge inter-conversion. Here, we report gate-tunable, ultrafast spin-to-charge current conversion in NiFe / LaAlO3 / SrTiO3, measured by THz emission spectroscopy. Upon ultrafast laser excitation, we found the sign of the emitted single-cycle THz pulses follows the direction of the magnetization in NiFe, and its magnitude decreases with increasing the thickness of the LaAlO3 layer. These findings support that the spin-charge conversion occurs at the LaAlO3 / SrTiO3 interface. Furthermore, we demonstrate that the amplitude of the emitted THz pulses can be tuned by electrostatic gating. Our findings extend ultrafast spin-charge conversion to oxides-based systems, thus providing a crucial link between ultrafast spintronics and correlated phenomena in complex oxides. |
Monday, March 5, 2018 5:06PM - 5:18PM |
C23.00010: Pressure tuning of coercivity states in quenched FeRh magnetic heterostructures Christian Urban, Steven P. Bennett, Ivan Schuller Control over coercivity of magnetic materials (e.g. Fe, Ni, Co) in bulk or thin films can be achieved by using compounds which undergo a structural phase transition[1,2]. The transition temperatures of these materials are sensitive to externally applied pressure. We show that this translates well to the coercivity change of the magnetic materials in close proximity which renders pressure an additional tuning parameter for the coercivity control. |
Monday, March 5, 2018 5:18PM - 5:30PM |
C23.00011: Spin-Torque Generation from Cu Oxides Yuito Kageyama, Yuya Tazaki, Hongyu An, Kazuya Ando Current-induced spin-orbit torques provide an effective way to manipulate the magnetization in spintronic devices, which promises ultralow energy consumption memory and logic devices. However, it has been believed that heavy metals are indispensable for generating the spin-orbit torques. Here, we report that Cu, which is an earth abundant light metal, generates sizable spin-orbit torques, triggered by precise tuning of the oxidation level. In this work, we investigate the generation efficiency of the spin-orbit torques from homogeneously oxidized Cu using the spin-torque ferromagnetic resonance (ST-FMR) technique for Ni81Fe19/CuOx bilayers. We demonstrate that the damping-like torque generated from CuOx is dramatically enhanced by the controlled oxidation only within a narrow range of the oxidation level, which is concomitant with the sign reversal of the field-like torque. We also show that the spin-orbit torques are generated from a highly oxidized Cu where a bulk charge current is negligible, indicating that interface spin-orbit coupling is responsible for the efficient spin-torque generation in this system. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700