Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session K40: Control of Magnetic OxidesFocus
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Sponsoring Units: GMAG DMP Chair: Chris Leighton, Univ of Minn - Minneapolis Room: BCEC 208 |
Wednesday, March 6, 2019 8:00AM - 8:36AM |
K40.00001: Control of Quantum States in 4d/5d Transition Metal Oxides* Invited Speaker: Gang Cao A delicate balance between spin-orbit and other competing interactions inherent in 4d/5d materials offers a unique range of opportunities to uncover exotic states and physical properties that are intimately coupled to the crystal structure [1]. This unique feature provides us fertile ground to control quantum states by tuning the lattice of single crystals. Here we present and discuss two recent examples and their fundamental significance: (i) Pressure-induced transition from interlayer ferromagnetism to intralayer antiferromagnetism in Sr4Ru3O10 [2], and (ii) Electrical-current control of structural and physical properties in canted antiferromagnetic iridates [3]. |
Wednesday, March 6, 2019 8:36AM - 8:48AM |
K40.00002: Electric field control of magnetic domains in Y-type hexaferrite single crystals at room temperature Vilmos Kocsis, Taro Nakajima, Masaaki Matsuda, Akiko Kikkawa, Yoshio Kaneko, Junya Takashima, Kazuhisa Kakurai, Taka-hisa Arima, Fumitaka Kagawa, Yusuke Tokunaga, Yoshinori Tokura, Yasujiro Taguchi In the trigonal Y-type hexaferrites the magnetoelectric properties are attributed to the emergence of the so-called FE3 phase with co-existing ferrimagnetic and ferroelectric orders [1]. Recently, in the Al-doped Y-type hexaferrite, (Ba,Sr)2Co2Fe11AlO22, this multiferroic phase has been observed as a metastable phase close to room temperatures even in the absence of magnetic field [2,3]. |
Wednesday, March 6, 2019 8:48AM - 9:00AM |
K40.00003: Magnetically Controlled Surface Acoustic Waves on Multiferroic BiFeO3 Ryo Sasaki, Yuta Ishii, Yoichi Nii, Toshimitsu Ito, Yoshinori Onose We fabricate a surface acoustic wave (SAW) device on a multiferroic BiFeO3 crystal while SAW devices are usually fabricated on nonmagnetic piezoelectrics and commercially available as bandpass filters. By using the time-domain technique, we demonstrate the SAW excitation on BiFeO3. The amplitude and phase of the SAW signal are modulated by the external magnetic field reflecting the multiferroicity of BiFeO3. The magnetic controllability of the multiferroic SAW device seems useful for the further functionalization of the SAW device. |
Wednesday, March 6, 2019 9:00AM - 9:12AM |
K40.00004: Pressure-induced magnetic behavior in Ca2Mn2O5-type A2B2O5 oxides Yongjin Shin, James M Rondinelli Brownmillerite oxides with the chemical formula A2B2O5 are derived from stoichiometric ABO3 perovskites and exhibit ordered oxygen vacancies (OOVs). The OOVs transform the octahedral BO6 units into different BO6-x polyhedra, which allows for large changes in the crystal field split orbital structure and subsequent changes in functional properties. The magnetic order of transition metal oxides is governed by the correlation between these orbitals and corresponding electronic configurations. For example, Sr2Mn2O5 (SMO; d4) in the Ca2Mn2O5-type square pyramidal network yields E-type antiferromagnetic (AFM-E) order, consistent with the Goodenough-Kanamori rules, whereas Sr2Fe2O5 (SFO; d5) exhibits AFM-G order within the same structure. Here, we investigate with first principles calculations the effect of hydrostatic pressure on the Ca2Mn2O5-type structure, which drives contrasting behavior in SMO and SFO. We show the AFM-E order in SMO is further stabilized under pressure while SFO exhibits a magnetic transition to a FM state at ~24 GPa arising from a spin crossover. Lastly, we evaluate the pressure effect induced by biaxial strain in OOV structures and discuss the feasibility of such phase transition in thin film geometries. |
Wednesday, March 6, 2019 9:12AM - 9:24AM |
K40.00005: Pressure-induced transition from an antiferromagnetic insulator to a ferromagnetic metal in Ca2Ru1-xMxO4 (M=Cr, Mn and Fe) Hao Zheng, Feng Ye, Songxue Chi, Hengdi Zhao, Yifei Ni, Yu Zhang, Gang Cao The comparable magnitudes of the Coulomb interaction and 4d-bandwidth can leave ruthenates precariously balanced on the border between metallic and insulating behavior, and/or on the verge of long-range magnetic order. Ca2RuO4 is an antiferromagnetic (AFM) Mott insulator with Neel temperature at TN = 110 K and a first-order metal-insulator transition at TMI = 357 K. It is recognized that Ca2RuO4 and its derivatives are highly sensitive to the lattice degrees of freedom. Here we report that application of modest pressure (< 2.5 GPa) readily destabilizes the AFM Mott state and precipitates a ferromagnetic metallic state at low temperatures in Ca2Ru1-xMxO4 (M=Cr, Mn and Fe). Transport and magnetic properties including neutron diffraction at pressure will be presented and discussed along with other related systems. |
Wednesday, March 6, 2019 9:24AM - 9:36AM |
K40.00006: Strain-induced heteronuclear charge disproportionation in EuMnO3 Ulrich Aschauer, Nathalie Vonrüti, Nicola Spaldin Charge disproportionation transitions commonly link high-temperature phases, in which cations of a given element have the same oxidation state, to low-temperature phases, where charge transfers between ions of this element results unequal oxidation states. Based on density functional theory calculations we here propose the concept of heteronuclear charge disproportionation, for which charge transfers occurs between different elements located on different crystallographic sites. Using EuMnO3 as a test case, we show that the transition from Eu3+Mn3+O3 to Eu2+Mn4+O3 can be triggered by pressure or epitaxial strain. We will highlight experimentally accessible signatures of this transition and discuss other crystal chemistries that could show similar phase transitions and resulting novel physics. |
Wednesday, March 6, 2019 9:36AM - 9:48AM |
K40.00007: Evidence of the Multiferroic Character of the EuO1-x -BaTiO3 Heterojunction Syed Qamar Abbas Shah, Gaurab Rimal, Guanhua Hao, Andrew J Yost, Jinke Tang, Peter A Dowben EuO1-x combines several interesting properties: large magneto-optical effects, colossal magneto-resistance, and enhanced Curie temperature due to bound magnetic polarons. EuO1-x is also one of a very few ferromagnetic insulators and, as an ultra thin film, very sensitive to interface effects. Investigation into the affect of ferroelectric substrates on the ferromagnetic properties of EuO1-x can provide deep insights into how one can manipulate magnetism by changing interface charge populations. Utilizing pulsed laser deposition, a thin film (20nm) of ferroelectric BaTiO3 was grown on top of a thin film (15nm) of ferromagnetic EuO1-x. X-ray diffraction indicates the presence of high quality crystalline thin films of EuO1-x and BaTiO3. Magneto optical Kerr effect (MOKE) spectroscopy and magneto-resistance measurements indicate a temperature dependent signature of anti-ferromagnetic magnetoelectric coupling of the ferroelectric/ferromagnetic heterostructure. This study sheds new light on the modulation of magnetoelectric coupling at a device interface. |
Wednesday, March 6, 2019 9:48AM - 10:00AM |
K40.00008: Magnetic structure of hexagonally stabilized (Lu,In)FeO3 Kwanghee Cho, Hakbeom Kim, Soonyong Park Hexagonal LuFeO3 has recently attracted considerable attention as promising candidates for room-temperature multiferroics, in which ferroelectricity and magnetism coexist in a single phase. However, most studies have been performed in a thin film form due to the instability of the bulk hexagonal LuFeO3. Herein, we report that in LuFeO3 a single hexagonal phase can be stabilized in both polycrystalline and single-crystalline bulk form with a wide range of Indium substitution in Lutetium site. Neutron diffraction results on magnetic spin structures and crystal structures of the Indium substituted LuFeO3 will be discussed. |
Wednesday, March 6, 2019 10:00AM - 10:12AM |
K40.00009: Meta—stability and Transient Phases Triggered by Optically Excited Quasi--particles in Strongly Correlated Systems. Myron Kapetanakis, Panagiotis Lingos, Jigang Wang, Ilias Perakis The interplay between electronic, magnetic and lattice degrees of freedom in colossal magnetoresistant manganites results in a rich phase diagram that provides an ideal model system for phase transition studies. Here we investigate the possibility of phase transitions induced by ultrafast optical laser pulses. We use a generalized tight—binding model, based on Hubbard operators, to describe the interaction between itinerant carrier and localized magnetic moment in multi--electron configurations. Optically—induced quasi—particle excitations introduce inhomogeneities, charge redistributions and spin fluctuations resulting in the formation of meta—stable states that trigger a non-equilibrium ultrafast dynamics. We discuss a theoretical description of optical switching mechanism between coexisting phases and highlight the role of photo—induced non—linearities on quantum femptosecond magnetism. |
Wednesday, March 6, 2019 10:12AM - 10:24AM |
K40.00010: ABSTRACT WITHDRAWN
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Wednesday, March 6, 2019 10:24AM - 10:36AM |
K40.00011: Modulating Charge-Orbital Ordering in SmBaMn2O6 Single Crystals with Tuneable Strain. Han Zhang, Lin Hao, Junyi Yang, Shua Sanchez, Jiun-Haw Chu, Haidong Zhou, Jian Liu SmBaMn2O6 is a perovskite manganese oxide with A-site ordering where competing interactions lead to a series of phase transitions. The observed orderings include charge-orbital-ordering, antiferromagnetic ordering, ferromagnetic canting and spin re-orientation. The Structural phase transition associated charge-orbital-ordering clearly indicate a strong relation between the lattice, charge and orbital. A systematic study with tunable strain along lattice directions is done to study how the latter two interact with lattice, as well as how the interplay contributes to the macroscopic properties. |
Wednesday, March 6, 2019 10:36AM - 10:48AM |
K40.00012: Field-induced antiferromagnetic cone structure in multiferroic BiFeO3 Masaaki Matsuda, Sachith Dissanayake, Yasuko Ozaki, Toshimitsu Ito, Xinzhi Liu, Maciej Bartkowiak, Oleksandr Prokhnenko BiFeO3, a rare multiferroic compound that shows antiferromagnetism and ferroelectricity simultaneously above room temperature (TN~640 K), has been studied intensively. Recently, a new magnetic phase has been found between the cycloidal and canted antiferromagnetic phase in magnetic field [1]. We performed neutron diffraction measurements in high static magnetic fields up to 19 T on HFM/EXED facility at BER II research reactor in Helmholtz Zentrum Berlin. We successfully observed weak incommensurate peaks around 13 T which split along the magnetic field direction [1,1,-2] at the (1/2, 1/2, 1/2) main peak. The magnetic field and temperature region, where the incommensurate peaks appear, is consistent with that in the phase diagram obtained by the magnetization measurements [1]. We confirmed that the magnetic structure in the intermediate phase is the antiferromagnetic cone structure which is predicted theoretically. We will show the detailed magnetic structure (magnetic wave vector and cone angle) and discuss the relation between the magnetic structure and the magnetoelectric effect. [1] S. Kawachi et al., Phys. Rev. Materials 1, 024408 (2017). |
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