Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session G49: Focus Session: Manganite and Cuprate Heterostructures |
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Sponsoring Units: DMP Chair: Bernhard Keimer, Max Planck Institute for Solid State Research Room: Mile High Ballroom 1C |
Tuesday, March 4, 2014 11:15AM - 11:51AM |
G49.00001: Unraveling electronic and magnetic structure at cuprate-manganite interfaces Invited Speaker: John Freeland Oxide interfaces offer a rich variety of physics and a pathway to create new classes of functional oxide materials. The interface between the cuprate high-temperature superconductors and ferromagnetic manganites is of particular interest due to the strongly antagonistic nature of the superconducting and ferromagnetic phases. Advancements in the synthesis of oxide heterostructure offers the opportunity to merge these two dissimilar oxides with atomic precision to understand the fundamental limits of bringing such states into close proximity. However, the main challenge is to understand the physical framework that describes the behavior of strongly correlated electrons near oxide interfaces. One aspect that will be addressed here is the use of advanced tools to gain detailed electronic and magnetic information from the boundary region[1-3]. In this talk, recent work will be addressed both in connection to visualizing the interface with spatially resolved tools [3] as well as harnessing layer-by-layer growth to explore the limits in ultrathin superlattices. These insights allow us to better understand the physics behind the interfacial spin and orbital reconstruction observed in this system [1,2]. Work at Argonne is supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.\\[4pt] [1] J. Chakhalian et. al. Nature Physics 2, 244 (2006). \\[0pt] [2] J. Chakhalian et. al. Science 318, 1114 (2007).\\[0pt] [3] Te-Yu Chien et al. Nature Communications 4 2236 (2013). [Preview Abstract] |
Tuesday, March 4, 2014 11:51AM - 12:03PM |
G49.00002: ABSTRACT WITHDRAWN |
Tuesday, March 4, 2014 12:03PM - 12:15PM |
G49.00003: Microstructural mechanism for attenuation of superconductivity in manganite/cuprate thin-film heterostructures J.Y.T. Wei, H. Zhang, N. Gauquelin, G.A. Botton Anomalously long-ranged proximity effects have recently been reported in manganite/cuprate heterostructures, and attributed to spin-triplet correlations for odd-frequency pairing. To elucidate this exotic scenario microscopically, we studied multilayer $\mathrm{La_{2/3}Ca_{1/3}MnO_3/YBa_2Cu_3O_{7-\delta}}$ (LCMO/YBCO) thin films using scanning transmission electron microscopy (STEM), x-ray diffraction (XRD) and electrical transport [1]. The atomic-scale STEM data revealed double CuO-chain intergrowths which effectively form regions with the 247 lattice structure in the YBCO layer. These nanoscale 247 regions do not show up in XRD, but can physically account for the reduction in superconducting critical temperature ($T_c$) as a function of YBCO thickness. We also observed similar $T_c$ reduction in $\mathrm{LaNiO_3/YBCO}$ heterostructures, where $\mathrm{LaNiO_3}$ is also epitaxially-matched with YBCO but is not ferromagnetic. These results suggest that microstructural defects, rather than magnetism, are responsible for the attenuation of superconductivity occuring in manganite/cuprate heterostructures. [1] H. Zhang \textit{et al.}, Appl. Phys. Lett. \textbf{103}, 052606 (2013). [Preview Abstract] |
Tuesday, March 4, 2014 12:15PM - 12:27PM |
G49.00004: Induced Ferromagnetism at Interfaces between BiFeO$_3$ and YBa$_2$Cu$_3$O$_7$ Jian-Xin Zhu, Xiao-Dong Wen, J.T. Haraldsen, C. Panagopoulos, E.E.M. Chia Transition metal oxides (TMOs) exhibit many emergent phenomena ranging from high-temperature superconductivity and giant magnetoresistance to magnetism and ferroelectricity. In addition, when TMOs are interfaced with each other, new functionalities can arise, which are absent in individual components. Here, we report results from first-principles calculations on the magnetism at the BiFeO$_3$/YBa$_2$Cu$_3$O$_7$ interfaces. By comparing the total energy for various magnetic spin configurations inside BiFeO$_3$, we are able to show that the ferromagnetism is induced near the interface. We further develop an interface exchange-coupling model and place the extracted exchange coupling interaction strengths from the first-principles calculations, into a resultant generic phase diagram. The emergence of interfacial ferromagnetism should have implications to electronic and transport properties. [Preview Abstract] |
Tuesday, March 4, 2014 12:27PM - 1:03PM |
G49.00005: Emergent Interfacial Ferromagnetism in CaMnO$_{3}$-based Superlattices Invited Speaker: Alexander Grutter Interfaces of complex oxide materials provide a rich playground not only for the exploration of properties not found in the bulk constituents but also for the development of functional interfaces to be incorporated in spintronic applications. Emergent interfacial magnetic phenomena have been of great interest but surprisingly there have been few examples of emergent interfacial ferromagnetism. In this talk, I will describe our recent work on the stabilization of ferromagnetism in CaMnO$_{3}$-based superlattices. We have demonstrated ferromagnetism at the interface between the antiferromagnetic insulator CaMnO$_{3}$ and a paramagnetic metallic layer, including CaRuO$_{3}$ and LaNiO$_{3}$. Theoretically the ferromagnetism has been attributed to an interfacial double exchange interaction among the interfacial Mn ions that is mediated by itinerant electrons from the paramagnetic metallic layer. Through polarized neutron reflectivity and observation of exchange bias, we have demonstrated that the ferromagnetism comes from Mn ions in a single unit cell at the interfaces just as theory has predicted. We have also demonstrated that the metallicity of the paramagnetic layer is critical in stabilizing ferromagnetism at the interface and that the interfacial ferromagnetism can be suppressed by suppressing the metallicity of the paramagnetic layer. Despite the agreement with theory, there remain open questions as to the magnetic interactions among the interfacial ferromagnetic layers. For example, the saturated magnetic moment modulates as a function of the thickness of both the CaMnO$_{3}$ and paramagnetic metal layers. The origins of this oscillation are not well understood and may stem from either structural effects or long-range oscillatory magnetic coupling interactions reminiscent of RKKY interactions. Evidence of the doubling of the unit cell and long range antiferromagnetic correlations support these speculations. [Preview Abstract] |
Tuesday, March 4, 2014 1:03PM - 1:15PM |
G49.00006: ABSTRACT WITHDRAWN |
Tuesday, March 4, 2014 1:15PM - 1:27PM |
G49.00007: Fabrication and Crystal Structure of [REMO$_{3}$ /ABO$_{3}$] (A$=$Ca, La, B$=$Fe, Mn, RE$=$Bi, La, M$=$Fe, Fe$_{0.8}$Mn$_{0.2})$ Superlattices Grown by Pulsed Laser Deposition Method K. Takase, Y. Watabe, N. Iwata, T. Oikawa, T. Hashimoto, M. Huijben, G. Rijnders, H. Yamamoto The superlattices of [REMO$_{3}$/ABO$_{3}$] (RE$=$Bi, La, M$=$Fe, Fe$_{0.8}$Mn$_{0.2}$ A$=$Ca, La, B$=$Fe, Mn) were prepared by Pulsed laser deposition (PLD) method grown on SrTiO$_{3}$(STO)(100) for the novel materials which show ferromagnetic and ferroelectric properties with giant magnetoelectric effect at room temperature. When the superlattices were prepared, seven units LaFeO$_{3}$(LFO) film was deposited first, and the required pulses for other materials to grow seven units were calculated using the growth rate ratio and the growth rate of the last three units of LFO. One of the superlattices, [7 units - BiFe$_{0.8}$Mn$_{0.2}$O$_{3}$(BFMO) / 7 units - CaMnO$_{3}$(CMO)] stacking for 14 times, the satellite peaks from -2 to $+$1 were observed. From the fitting to the X-ray reflection spectra, thickness of BFMO and CMO in [BFMO/CMO] one cycle was 2.139nm (5.3 units) and 2.042nm (5.5 units). Although the deposited number of units was definitely less than seven, the satellite peaks are derived from the superstructure. Reciprocal space mapping shows the \textit{in-plain} lattice constant of [BFMO/CMO] superlattices was not fitted to that of substrate. The calculated \textit{in-plain} lattice parameter was 0.382 nm longer than the value of 0.3732 nm, which is the bulk CMO and \textit{in-plain} lattice parameter of CMO thin film grown on STO(001) substrate. [Preview Abstract] |
Tuesday, March 4, 2014 1:27PM - 1:39PM |
G49.00008: Interface-Induced Magnetic Coupling in Multiferroic/Ferromagnetic Bilayer: An Ultrafast Pump-Probe Study Elbert Chia, Chan La-o-vorakiat, Y.F. Tian, Tom Wu, Christos Panagopoulos, Jian-Xin Zhu, Haibin Su By use of optical pump-probe measurement, we study the relaxation dynamics of a muliferroic-ferromagnetic TbMnO$_{3}$/La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ bilayer. The relaxation dynamics of both layers are well separated in time allowing us to investigate the magnetic coupling across the bilayer. We observe that the relaxation dynamics of the individual layers in the bilayer sample are the result of the interplay between the intrinsic magnetic order and the induced interfacial effect. Our data suggest the existence of induced ferromagnetic order in the TbMnO$_{3}$ layer, and antiferromagnetic order in the La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ layer. [Preview Abstract] |
Tuesday, March 4, 2014 1:39PM - 1:51PM |
G49.00009: Control of magnetism by tuning interfacial octahedral rotations in atomic-layer superlattices Xiaofang Zhai, Long Cheng, Yang Liu, Christian Schleputz, Hui Li, Xiaoqiang Zhang, Shengqi Chu, Lirong Zheng, Jing Zhang, Aidi Zhao, Hawoong Hong, Anand Bhattacharya, James Eckstein, Changgan Zeng It was recently predicted that structural reconstructions caused by discontinuities in the oxygen octahedral rotation (OOR) patterns at complex oxides interfaces are capable of shaping interface magnetic properties. However, experimental evidences for this interrelation are scarce. By combining state-of-the-art laser molecular-beam-epitaxy and synchrotron X-ray diffraction techniques, we demonstrate that interfacial OOR are closely linked to the strongly modified ferromagnetism (FM) in (LaMnO3plusd)N/(SrTiO3)N superlattices. The maximized FM moment in the N$=$6 superlattice is accompanied by charge-transfer and a metastable structure (Imcm) featuring minimal octahedral rotations. Quenched FM for N smaller than 4 superlattices is attributed to a substantially enhanced c-axis octahedral rotation (about 8 deg), a phenomenon that has been predicted theoretically but never observed experimentally. Our study demonstrates that engineering superlattices with controllable interfacial structures may be a new route in realizing functional magnetic materials. [Preview Abstract] |
Tuesday, March 4, 2014 1:51PM - 2:03PM |
G49.00010: What EELS Spectra Tell Us About Manganite/ferroelectric Interfaces: Ab Initio Results Alexandru Bogdan Georgescu, M.S.J. Marshall, A. Gulec, P.J. Philips, R.F. Klie, F.J. Walker, C.H. Ahn, Sohrab Ismail-Beigi The interplay of structure, electronic states, and magnetism is a rich field of research for transition metal oxides. Manganese oxides are well known for the dependence of their magnetic state and resistivity on doping (colossal magnetoresistance) which can be modified by chemical alloying or dynamically via the ferroelectric field effect. We focus on the interface between an oxide ferroelectric and the manganite La$_x$Sr$_{1-x}$MnO$_3$ where it has already been established that there is a dramatic coupling of atomic geometry, electronic structure and magnetism which leads to a very large magnetoelectric coupling. In this work, we use first principles theory to understand what observed atomically-resolved EELS spectra on such systems tell us about the interfacial structure and electronic properties. By understanding the link between EELS and atomic-scale structure at an oxide interface, one can then more confidently interpret experimental results to understand interfaces of novel materials, particularly correlated electron systems. [Preview Abstract] |
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