Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session R20: Focus Session: Multiferroics III: Perovskites |
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Sponsoring Units: DMP GMAG Chair: Craig Fennie, Rutgers University Room: Baltimore Convention Center 317 |
Wednesday, March 15, 2006 2:30PM - 2:42PM |
R20.00001: Multiferroicity of BiMnO$_3$ reexamined from first principles. Tatsuya Shishidou, Tamio Oguchi BiMnO$_3$ is believed to show both ferromagnetic and ferroelectric orders. In contrast to its robustly confirmed ferromagnetism, only one experimental group has succeeded in observing ferroelectric hysteresis loop[1]. Another group has reported small magnetocapacitance effect around the ferromagnetic Curie temperature[2]. Using first-principles scalar-relativistic full-potential linear augmented plane wave (FLAPW) method and adopting the experimental lattice data, we have given several significant insights on physical properties of BiMnO$_3$[3]. Further extended results will be shown in this talk. With including spin-orbit interaction, possible directional coupling between the polarization and magnetization will be discussed together with magnetocrystalline anisotropy. Results of structual optimization based on the first-principles atomic forces will be presented to verify its ferroelectricity. Possible doping effect will also be explored. [1] A.~Moreira dos Santos {\it et al.}, Solid State Commun.\ {\bf 122} 49 (2002). [2] T.~Kimura {\it et al.}, Phys.\ Rev.\ B {\bf 67} 180401(R) (2003). [3] T.~Shishidou, N.~Mikamo, Y.~Uratani, F.~Ishii, and T.~Oguchi, J.\ Phys.: Condens.\ Matter {\bf 16} S5677 (2004). [Preview Abstract] |
Wednesday, March 15, 2006 2:42PM - 2:54PM |
R20.00002: Orbital order, ferromagnetism, and ferroelectricity of BiMnO$_3$ and related compounds Chanho Yang, Taeyeong Koo, Yoon Hee Jeong Multiferroic materials, where ferroelectricity and magnetism coexist, have been actively studied. This class of materials would offer a large application potential for new devices taking advantage of two coupled degrees of freedom based on local off-centered distortion and electron spin. Although most often the magnetic state in coexistence with ferroelectricity is antiferromagnetic, BiMnO$_3$ is an interesting exception with the simultaneous existence of ferromagnetism and ferroelectricity. However, the transition temperatures are in great disparity with T$_{FE}$ = 770 K and T$_{FM}$ = 105 K, and consequently its ME coupling is not large. In this talk, we will report on three aspects of BiMnO$_3$: (1) Long range ordering of 3d-orbital of Mn$^{3+}$ ions and its influence to the ferromagnetism and ferroelectricity (2) How to create a system to induce a large inter- property coupling by modifying BiMnO$_3$ (3) How to obtain a material with a large inter-coupling at room temperature [Preview Abstract] |
Wednesday, March 15, 2006 2:54PM - 3:06PM |
R20.00003: Magnetic Ferroelectrics Bi,Pb-3$d$ Transition Metal Perovskites Masaki Azuma, Kazuhide Takata, Takashi Saito, Yuichi Shimakawa, Mikio Takano, Seiji Niitaka, Alexei Belik, Shintaro Ishiwata Magnetic ferroelectrics attract much attention because of the possible application for the memory device and the fascinating coupling between magnetic and dielectric properties. A classical way to obtain a magnetic ferroelectric is to locate Bi$^{3+}$ or Pb$^{2+ }$ions and a magnetic transition metal ion on A and B sites of perovskite structure. The 6s$^{2}$ lone pair and the strong covalent character of Bi(Pb)-O bonds stabilize a noncentrosymmetric distorted structure. For example, BiFeO$_{3}$ and BiMnO$_{3}$ are established antiferromagnetic and ferromagnetic ferroelectrics, respectively. We have studied structure, magnetic and electric properties of Bi$M$O$_{3}$ with $M$=Cr, Co and Ni and PbVO$_{3}$ stabilized by high-pressure synthesis. BiCrO$_{3}$ is an antiferromagnetic ferroelectric with BiMnO$_{3}$ type structure. BiCoO$_{3}$ and PbVO$_{3}$ are found to have tetragonal PbTiO$_{3}$ type structures with expected polarizations of $\sim $100$\mu $C/cm$^{2}$. BiNiO$_{3 }$crystallizes in a triclinic structure where disproportionation into Bi$^{3+}$ and Bi$^{5+}$ takes place. We have also succeeded in preparing a designed ferromagnetic ferroelectric double provskite Bi$_{2}$NiMnO$_{6}$. In this compound, NaCl type ordering of Ni$^{2+}$ ($e_{g}^{1})$ and Mn$^{4+}$ ($t_{2g}^{3})$ leads to ferromagnetism with $T_{C}$=140 K. [Preview Abstract] |
Wednesday, March 15, 2006 3:06PM - 3:18PM |
R20.00004: Dielectric, magnetic, magneto-optical and nonlinear optical properties of ferroelectric ferromagnetic semiconductor BiMnO$_{3}$ from first-principles calculations Guang-Yu Guo, Hai-Qing Lin BiMnO$_{3}$ is a biferroic (ferroelectric and ferromagnetic) semiconductor, and hence a member of the family of multiferroic materials. In order to gain a full understanding of its interesting properties such as biferroic behavior, we have calculated from first-principles the electronic structure, exchange coupling, linear and non-linear optical susceptibilities as well as magneto-optical Kerr rotation of BiMnO$_{3}$. The calculations are based on density functional theory with generalized gradient approximation plus on-site Coulomb correlation (GGA+U). The all-electron full potential linearized augmented plane wave (FLAPW), frozen core full potential projector augmented wave (PAW), and also all-electron tight-binding linear muffin-tin orbital methods (TB-LMTO) are used. In this contribution, we will present and analyze the obtained exchange coupling parameters, magneto-optical Kerr rotation spectra, dielectric constants and second-harmonic generation coefficients. [Preview Abstract] |
Wednesday, March 15, 2006 3:18PM - 3:30PM |
R20.00005: Properties and superlattice for multiferroics BiMnO$_{3}$ . C.Q. Jin, Z.H. Chi, H. Yang, R.C. Yu, S.M. Feng, F. Y. Li Single-phase multiferroics BiMnO$_{3 }$ceramic was synthesized via high-pressure high-temperature technique. Microstructure modification accompanied by emergence of superlattice due to electron-beam irradiation was observed wherein by means of ED and HRTEM. Magnetic evaluation manifesting a unique ferromagnetic phase transition at 103 K has corroborated our speculation that as-prepared BiMnO3 ceramic is free of polymorphism at room temperature. Furthermore, magnetization versus temperature ($M-T)$ characterization combined with \textit{in situ} variable temperature powder X-ray diffraction (XRD) and dielectric constant versus temperature (\textit{$\varepsilon $-T}) spectrum scanning confirmed that as-prepared BiMnO$_{3}$ specimen exhibits simultaneous occurrence of ferromagnetism and ferroelectricity below its ferromagnetic Curie temperature ($T_{M})_{ }$of 103 K. . [Preview Abstract] |
Wednesday, March 15, 2006 3:30PM - 3:42PM |
R20.00006: Structural Investigations of Bi-containing, multiferroic thin films using Second Harmonic Generation Ernst Knoesel, S.E. Lofland, K.F. McDonald, C.J. Meeting, M. Murakami, M. Aranova, I. Takeuchi The intensity and polarisation of the bulk second harmonic generation (SHG) from thin films depends critically on the second-order susceptibility tensor, which in turn is strongly influenced by the crystal structure of the film. Multiferroic BiMO$_{3}$ (M=Fe,Cr) thin films were grown epitaxially as thin films on varies substrates with changing orientations. We have found a substantial bulk SHG signal from of these materials and performed comparative magnetic field and temperature dependent studies. The implication with respect to crystal structure, magnetic phase transitions and multiferroic properties are discussed. [Preview Abstract] |
Wednesday, March 15, 2006 3:42PM - 3:54PM |
R20.00007: Multiphase Formation In Bi based Multiferroic Thin Films: Structural Change And Strain Relaxation Sung Hwan Lim, Makoto Murakami, Shigehiro Fujino, Manfred Wuttig, Ichiro Takeuchi, Lourdes G. Salamanca-Riba, Wendy Lynn Sarney Bi based multiferroic epitaxial thin films like, Bi-Fe-O and Bi-Mn-O were grown on SrTiO$_{3}$(001) substrates by pulsed laser deposition under various oxygen partial pressures (0.1 -- 20 mTorr) and thickness (35 -- 500 nm). The structural properties of impurity phases in these systems were characterized by transmission electron microscopy, x-ray diffraction, and energy dispersive x-ray spectroscopy. In the Bi-Fe-O system growth at oxygen partial pressures lower than 5 mTorr gives rise to the formation of the canted antiferromagnetic phase, $\alpha $-Fe$_{2}$O$_{3}$ with a columnar structure in a matrix of BiFeO$_{3}$. Simultaneously, ferromagnetic phase, $\gamma $-Fe$_{2}$O$_{3}$ precipitates with plate-like structure in the $\alpha $-Fe$_{2}$O$_{3}$ matrix. Similarly, Mn$_{3}$O$_{4}$ impurity phase forms in the Bi-Mn-O system when the films are grown at low oxygen partial pressure. In Bi-Fe-O film, the friction of $\gamma $-Fe$_{2}$O$_{3}$ enhances the magnetic properties of the film, while $\alpha $-Fe$_{2}$O$_{3}$ reduces the compressive stress in BiFeO$_{3}$ due to its smaller volume compared to that of BiFeO$_{3}$. We also report structural and magnetic properties of BiCrO$_{3}$ thin film, a new multiferroic material. [Preview Abstract] |
Wednesday, March 15, 2006 3:54PM - 4:06PM |
R20.00008: Dichroism and order parameter coupling in BiFeO$_3$ Films Mikel Barry, T. Zhao, F. Zavaliche, M.P. Cruz, Y.H. Chu, R. Ramesh, A. Scholl, A. Doran BiFeO$_3$ is an attractive material because it is a possible multiferroic and lead-free replacement for ferroelectric memory cells and piezoelectric sensors and actuators. We are probing the possibility of coupling between ferroelectricity and antiferromagnetism in epitaxial thin films of this system. X-ray linear dichroism based PEEM images were obtained using a high spatial resolution photoelectron emission microscope (PEEM). This combination of XLD and PEEM provides high spatial resolution along with elemental and chemical specificity and surface sensitivity. A Piezoforce microscope (PFM) was used to switch the ferroelectric state in micron-sized regions of the film, which were subsequently probed using temperature dependent PEEM measurements. Temperature dependent structural measurements were carried out to probe the changes in the ferroelectric order parameter with temperature. We observe a strong change in XLD as the temperature is raised to and beyond the Neel temperature. We will present the results of our approaches to decouple the XLD responses that arise from purely the structural distortion (i.e., due to ferroelectricity) and that arising from the antiferromagnetic state, as well as the results of the coupling experiments. This work is supported by an LBL-LDRD program and by the ONR under a MURI program. [Preview Abstract] |
Wednesday, March 15, 2006 4:06PM - 4:18PM |
R20.00009: Systematic investigation of multiferroic properties of (Bi$_{1-x}$Sm$_{x})$FeO$_{3}$ and (Bi$_{1-x}$La$_{x})$FeO$_{3}$ thin films using composition spreads Makoto Murakami, V. Nagarajan, A. Vartharajan, S. Fujino, M. Wuttig, I. Takeuchi BiFeO$_{3}$ and its room temperature multiferroic properties have attracted much attention. However, it is generally believed that its magnetic and ferroelectric properties have not been unambiguously established. There have been some reports of A-site substituted BiFeO$_{3}$ aimed at improving its properties. In this study, we report on synthesis and multiferroic properties of La and Sm modified BiFeO$_{3}$ thin films. In particular, in order to systematically study these systems, we fabricated composition spread thin films of (Bi$_{1-x}$Sm$_{x})$FeO$_{3}$ and (Bi$_{1-x}$La$_{x})$FeO$_{3}$ (x=0$\sim $1) on SrTiO$_{3}$ and LaAlO$_{3}$ substrates using combinatorial pulsed laser deposition. Several structural transitions were found in the middle of the spreads in both systems using x-ray microdiffraction. In (Bi$_{1-x}$La$_{x})$FeO$_{3}$, the structure was found to change from rhombohedral to paramagnetic phase at about 20{\%} of BiFeO$_{3}$. Ferroelectric properties and magnetic properties of the spreads were mapped using piezoforce microscopy and scanning SQUID microscopy. We report on the effect of the structural transitions on their multiferroic properties. This work was supported by NSF MRSEC DMR 0520471 and ONR. [Preview Abstract] |
Wednesday, March 15, 2006 4:18PM - 4:30PM |
R20.00010: Scanning probe imaging of coexistent ferroelectricity and ferromagnetism in thin films of room temperature multiferroics. V.R. Palkar, S.C. Purandare, J. John, S. Gohil, S. Bhattacharya Scanning probe imaging methods, both piezoresponse and magnetic force types, are used to study domain patterns in thin films of room temperature multiferroics. The results demonstrate coexistence of the two order parameters in microscopic scale and rules out macroscopic phase separation. Furthermore, a tapping mode technique is shown to yield information of both order parameters allowing simultaneous observation of both types of domain structures. Prospects of imaging possible coupling between the two order parameters, as seen in bulk measurements, will be discussed. [Preview Abstract] |
Wednesday, March 15, 2006 4:30PM - 4:42PM |
R20.00011: The Nanostructure Formation and Growth Evolution of Ferroelectric/Ferromagnetic BiFeO$_{3}$-CoFe$_{2}$O$_{4}$ Thin Films Sheng Yu Young, Lourdes G. Salamanca-Riba, Haimei Zheng We have investigated the mechanism of the self-assembly of BiFeO$_{3}$-CoFe$_{2}$O$_{4}$ (BFO-CFO) ferroelectric/ferromagnetic thin film nanostructures using high-resolution transmission electron microscopy. We discuss the formation of the CFO columnar structure during the deposition process. The BFO-CFO thin films were deposited on SrTiO$_{3}$ (001) single crystal substrates using pulsed laser deposition at a substrate temperature of 700 $^{o}$C and deposition rate of around 5nm/min. In the early stages of growth, CFO domains form with dome like island shape and are covered by a BFO layer. After approximately 10 mins of continuous deposition, the nanocomposite rearranges and diffusion dominates to form a self-assembly of faceted CFO columns that extend to the surface of the film. These columns show pyramidal-like faceted shape and are embedded in the BFO matrix. A few atomic layers of BFO lie at the interface between the CFO columnar structures and the substrate. This layer helps relax the misfit strain between CFO and STO. The magnetic properties of the nanocomposite samples will also be presented. [Preview Abstract] |
Wednesday, March 15, 2006 4:42PM - 4:54PM |
R20.00012: Electrical and Magnetic Properties of Pb(Zr,Ti)O$_{3}$/CoFe$_{2}$O$_{4}$ Composite Thin Films Nora Ortega, S. Majumder, P. Bhattacharya, R.S. Katiyar, P. Dutta, M.S. Seehra, A. Manivannan Composite thin films made of ferroelectric and ferromagnetic materials are the potential candidates for sensors, data storage, and transducers due to possible manipulation of magnetic properties by electric field and vice versa. In this work, we have fabricated Pb(Zr,Ti)O$_{3}$--CoFe$_{2}$O$_{4}$ (PZT-CFO) multilayer thin films using pulsed laser deposition on Pt/TiO$_{2}$/SiO$_{2}$/Si substrates at 400 \r{ }C and post annealed at 650\r{ }C using rapid thermal annealing (RTA) process. The X-ray diffraction studies revealed the growth of the perovskite PZT and the spinel CFO in two separated phases in the composite films. The dielectric constant ($\varepsilon _{r})$ of PZT-CFO multilayer showed strong frequency dispersion with an order of magnitude decrease in the frequency range of 1kHz to 1MHz. Similar decrease in $\varepsilon _{r}$ was also observed with decrease of temperature from 300 to 150 K. The remanent polarization (P$_{r})$ of the film (23 $\mu $C/cm$^{2})$ was also reduced to 1 $\mu $C/cm$^{2 }$with decrease in the temperature (at 100 K). The magnetic measurements in the composite thin films showed the saturation magnetization (M$_{s})$ to be 9 emu/cm$^{3}$ at room temperature that increased to 38 emu/cm$^{3}$ at 5 K. [Preview Abstract] |
Wednesday, March 15, 2006 4:54PM - 5:06PM |
R20.00013: Quantum Monte Carlo calculations of BiScO$_{3}$ ferroelectric well-depths Hendra Kwee, Henry Krakauer, Shiwei Zhang The perovskite (1-x) BiScO$_{3}$-x PbTiO$_{3}$ alloy has been reported as having a large piezoelectric properties.\footnote {R.E. Eitel, {\it et al.}, {\it Jpn. J. Appl. Phys.}, Part 1 {\bf 40},5999 (2001); R.E. Eitel, {\it et al.}, ibid. {\bf 41}, 1 (2002)} Density functional theory (DFT) using local density approximation (LDA) predicts an extraordinarily large ferroelectric well depths (about 1.2 eV) of the end point compound BiScO$_{3}$.\footnote {J. \'{I}\~{n}iquez, D. Vanderbilt, L. Bellaiche, Phys. Rev B {\bf 67}, 224107 (2003)} We perform quantum Monte Carlo calculations on BiScO$_{3}$ to calculate these well depths. In our QMC method,\footnote{S. Zhang, H. Krakauer, Phys. Rev. Lett {\bf 90}, 136401 (2003)} the two-body terms coming from electron-electron interactions are decoupled using a Hubbard- Stratonovich transformation. The ground state is obtained from projection of an initial trial wave function by random walks in Slater determinant space. To control the sign/phase problem, a trial Slater determinant is used, which in our calculations is taken directly from the DFT calculations. We find in the QMC calculation large finite-size effects in the primitive cell, on the order of a few eV. We study these finite-size effects and explore several schemes to reduce them. [Preview Abstract] |
Wednesday, March 15, 2006 5:06PM - 5:18PM |
R20.00014: Magnetic and structural properties of CeO$_{2}$ nanoparticles Prasanta Dutta, Susmita Pal, Mohindar Seehra, G. Turpin, R. Ernst Nanoparticles of cerium oxide, CeO$_{2}$, have potential applications in catalysis, fuel cells, microelectronics etc [1]. In this work, we have investigated the magnetic and structural properties of 10{\%}CeO$_{2}$ supported on SiO$_{2}$ aerogel with a BET surface area $\approx $ 700 m$^{2}$/g. X-ray diffraction (XRD) studies show cubic CeO$_{2}$ as the dominant phase with particle size $\approx $ 3 nm. Temperature variation (2K -- 350K) of the magnetic susceptibility $\chi $ shows Curie-type variation with the Curie constant C = 5.9 $\times $ 10$^{-5}$ emu K/g Oe. In electron magnetic resonance (EMR) studies from 5 K to 300 K at 9.28 GHz, an EMR line at g $\approx $ 2.1 with linewidth $\Delta $H $\approx $ 100 Oe is observed for T $<$ 40 K. Since Ce$^{4+}$ in CeO$_{2}$ is diamagnetic, we tentatively suggest that the observed Curie variation of $\chi $ and the EMR line [2] are due to paramagnetic Ce$^{3+}$ present in oxygen-lean CeO$_ {2}$ nanoparticles. From the magnitude of C, the concentration of Ce$^{3+}$ is estimated to be $\approx $ 3 {\%}. Further studies are in progress. [1]. S. Sathyamurthy et al, Nanotechnol. \underline {16}, 1960 (2005). [2]. D. Schaniel et al, Phys. Rev. B \underline {70,} 144410 (2004). [Preview Abstract] |
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