Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session Y36: Focus Session: Bulk Properties of Complex Oxides -- General Multiferroics |
Hide Abstracts |
Sponsoring Units: DMP GMAG Chair: Gavin Lawes, Wayne State University Room: E146 |
Friday, March 19, 2010 8:00AM - 8:12AM |
Y36.00001: Modifying phase transitions and spin structure of Ni$_{3}$V$_{2}$O$_{8}$ through transition metal doping Akila Kumarasiri, Parashu Kharel, Ambesh Dixit, Mike Nowak, Gavin Lawes Ni$_{3}$V$_{2}$O$_{8}$ is a Kagome staircase material which has attracted considerable interest in recent years as it provides an excellent platform for studying the spin structure in geometrically frustrated materials. We have studied the effects of transition metal doping on the magnetic phase transitions of powder Ni$_{3}$V$_{2}$O$_{8}$ through dielectric, heat capacity and AC susceptibility measurements. (Ni$_{1-x}$M$_{x})_{3}$V$_{2}$O$_{8}$ (M = Zn, Cu and Co) powder samples were synthesized using a standard metal-organic solution synthesis. We have mainly focused on the two phase transitions at T$_{H}$ = 9.2 K and T$_{L}$ = 6.3 K in undoped Ni$_{3}$V$_{2}$O$_{8}$. On doping with non magnetic Zn, the system acts similar to spin dilution where the transition temperatures is suppressed linearly with the Zn fraction. However, spin 1/2 Cu and spin 3/2 Co doping shows significant deviation from simple site dilution. The Co:Ni$_{3}$V$_{2}$O$_{8}$ system has a crossover at moderate Co fraction where the system changes into a Co$_{3}$V$_{2}$O$_{8}$ type spin structure. Cu doping completely suppresses at least one phase transition at a relatively low Cu fraction. [Preview Abstract] |
Friday, March 19, 2010 8:12AM - 8:24AM |
Y36.00002: Functionally Graded Composite Multiferroics and Magnetoelectric Interactions G. Sreenivasulu, S.K. Mandal, V.M. Petrov, G. Srinivasan This work is on (i) synthesis of functionally stepped or graded ferrite-ferroelectric bilayers and (ii) investigations on the nature of magneto-electric (ME) interactions. The parameters of importance for grading are the piezomagnetic coefficient $q$ and piezoelectric coefficient $d$ that determine the strength of ME coupling. Recent theories predict strong ME interactions in graded systems. Bilayer and trilayers of nickel cobalt ferrite-lead zirconate titanate were studied. Grading of $q$ was accomplished by compositional variation of the ferrite and grading of $d$ was achieved by poling the piezoelectric layers in opposite directions. Studies on low-frequency and resonant ME -- coupling reveal strong ME effects in graded systems. -- work supported by grants from DARPA and NSF. [Preview Abstract] |
Friday, March 19, 2010 8:24AM - 9:00AM |
Y36.00003: GMAG Student Award Talk: Effects of high pressure, magnetic fields and substitutions on multiferroic systems Invited Speaker: We have investigated various materials with regard to the effects of pressure, field, and substitution on their multiferroic properties. In MnWO$_{4}$ we find that replacement of Mn$^{+2}$ by Fe$^{+2}$ or Zn$^{+2}$ ions results in the suppression (Fe) or enhancement (Zn) of the ferroelectric (FE) phase. Novel effects are observed in external magnetic fields (H), for example the field-induced re--entrant FE/spiral magnetic phase in Mn$_{1-x}$Fe$_{x}$WO$_{4}$. The complete x-H-T phase diagrams are constructed for these compounds from polarization, dielectric constant, specific heat and magnetization data. The anisotropic Heisenberg model was solved to qualitatively understand the effects of substitution and field. The sensitivity of the FE polarization under high pressure was investigated. Pressure does suppress the FE polarization of Ni$_{3}$V$_{2}$O$_{8}$ and MnWO$_{4}$. In YMn$_{2}$O$_{5}$, however, external pressure did reverse the FE polarization at low T. We have conducted high resolution thermal expansion measurements revealing significant lattice anomalies and correlated these results with the observed pressure effects. [Preview Abstract] |
Friday, March 19, 2010 9:00AM - 9:12AM |
Y36.00004: Dielectric anomaly and structural change related to the Jahn-Teller transition in DyVO$_{4}$ Kazumasa Kishimoto, Taishi Ishikura, Hiroyuki Nakamura, Yusuke Wakabayashi, Tsuyoshi Kimura $R$VO$_{4}$ system has been studied as dielectrics for several decades. Among them, DyVO$_{4}$ having Dy$^{3+}$ ( 4$f^{9})$ and V$^{5+}$ (3$d^{0})$ ions shows the Jahn-Teller (JT) transition at $T_{D}$ =14 K due to the interaction between 4$f$ electrons on Dy sites and the lattice. As a result, the lattice distorts from the $I$4$_{1}$\textit{amd} tetragonal to the \textit{Imma} orthorhombic structure and ferroquadrupolar ordering occurs below $T_{D}$. We measured the dielectric constant of a single crystal of DyVO$_{4}$ and observed a distinct dielectric anomaly around $T_{D}$. To clarify the origin of the dielectric anomaly, we performed detailed single crystal structure analyses. Our results suggest that the JT distortion shifts the position of oxygen ions relative to a V ion and then local polarization of a VO$_{4}$ tetrahedron is induced below $T_{D}$. We also report the structural domain control causing remarkable magnetocapacitance effects by applying a relatively small magnetic field ($\sim $0.1 T), which is attributed to the strong spin-orbit coupling of Dy 4$f$ electrons. [Preview Abstract] |
Friday, March 19, 2010 9:12AM - 9:24AM |
Y36.00005: Magnetic and ferroelectric properties of bulk and thin film FeVO$_{4}$ Gavin Lawes, Ambesh Dixit The development of ferroelectric order at a magnetic phase transition is a particularly striking example of the strong coupling that can arise between charge and spin degrees of freedom. We present results on the magnetic, electrical, dielectric, optical, and thermodyamic characterization of FeVO$_{4}$ ceramic and thin film samples. This system has two low temperature phase transitions at T=22 K and T=15 K, with ferroelectric order developing at the lower temperature transition. The polarization at this transition is only 6 $\mu $C/m$^{2}$ in the bulk polycrystalline sample, although we believe the intrinsic polarization could be as large as 40 $\mu $C/m$^{2}$ without powder averaging. There are distinct shifts in certain Raman peaks in the narrow temperature range between the two magnetic phase transitions, which may be related to the development of ferroelectric order. The T=15 K phase transition shifts to lower temperatures with the application of an external magnetic field but, in the thin film sample, shifts to higher temperatures with the application of an external electric field. This electric field control of a magnetic transition confirms the strong coupling between ferroelectricity and magnetism in this system. [Preview Abstract] |
Friday, March 19, 2010 9:24AM - 9:36AM |
Y36.00006: ABSTRACT WITHDRAWN |
Friday, March 19, 2010 9:36AM - 9:48AM |
Y36.00007: Optical Properties of the Multiferroic Crystal Cu2OSeO3 Kevin Miller, David Tanner, Daniel Arenas, Helmuth Berger Reflectivity as a function of temperature has been measured on the multiferroic crystal Cu2OSeO3 utilizing light spanning the far infrared to the visible portions of the electromagnetic spectrum. The complex dielectric function was obtained via Kramers-Kronig analysis. The optical properties as well as the dynamics of particular phonon modes have been monitored through the magnetic phase transition temperature (Tc=60K). Tentative assignments have also been made to the strong far infrared phonon modes. [Preview Abstract] |
Friday, March 19, 2010 9:48AM - 10:00AM |
Y36.00008: Magnetodielectric Coupling in CoSeO$_4$ Brent Melot, Ram Seshadri, Abby Goldman, Efrain Rodriguez We investigate the magnetic phase diagram and magnetodielectric properties of CoSeO$_4$, a material which contains chains of edge-sharing octahedral Co(II) connected by tetrahedral SeO$_4$ units. Specific heat measurements in combination with powder neutron diffraction show a transition to long-range magnetic order below 30\,K. Fits to the high temperature susceptibility give a Curie-Weiss temperature of -35\,K, indicating the magnetic ground state has a dominant antiferromagnetic ordering. However, magnetization measurements in a field of 100 Oe also indicate the presence of weak ferromagnetism and a field-induced transition in fields larger than 30 kOe. The zero-field magnetic structure consists of Co moments aligning antiparallel to nearest neighbors down the length of the chains. We also present evidence of a linear magnetoelectric response in the ground state magnetic phase. [Preview Abstract] |
Friday, March 19, 2010 10:00AM - 10:12AM |
Y36.00009: Polarization-modulated rectification at ferroelectric surfaces Weida Wu, Y. Horibe, S. Park, T. Choi, S.-W. Cheong, S.B. Kim, J.R. Guest, M. Bode By correlating room temperature conductive atomic force microscopy (c-AFM) with low temperature electrostatic force microscopy (EFM) images taken at different temperatures but the same location, we demonstrate that nanoscale electric conduction between a sharp tip and the surface of ferroelectric HoMnO$_3$ is intrinsically modulated by the polarization of ferroelectric domains. Conductance spectra reveal that the electric conduction is described by polarization-induced Schottky-like rectification at low bias, but dominated by a space-charge limited conduction mechanism at high bias. Our observation demonstrates visualization ferroelectric domain structure by electric conduction, which may be used for non-destructive read-out of nanoscale ferroelectric memories or sensors. [Preview Abstract] |
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