Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session P33: Focus Session: Dielectric, Ferroelectric, and Piezoelectric Oxides: BiFeO3 |
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Sponsoring Units: DMP DCOMP Chair: Nicole Benedek, Cornell University Room: C143/149 |
Wednesday, March 23, 2011 8:00AM - 8:12AM |
P33.00001: Manipulation of the domain structure in mixed-phase BiFeO3 epitaxial films Yi-Chun Chen, Hsin-Hua Lee, Feng-Nan Chu, Wen-Chuan Hsieh, Q. He, Wen-I Liang, Ying-Hao Chu Strain-induced phase transformation in epitaxial films is the newly advance in thin-film growth techniques. Under the compressive strain from the substrate, the stable phase of multiferroic BiFeO3 (BFO) films transformed from rhombohedrally- to tetragonally- distorted monoclinic perovskite, which simulated the material system near the morphotropic phase boundary. In this study, we used piezoresponse force microscopy (PFM) to investigate the intrinsic domain structures in the mixed-phase BFO epitaxial films. PFM taken along the principal crystallographic directions revealed the domain polarizations. The IP PFM images indicated the coexistence of at least two monoclinic phases with IP distortions along [100] and [110]. The domains were distributed in the way to minimize the local electrostatic energy, and the mixed phase pattern can be effectively controlled by external fields. The dynamic switching parameters for the domain and phase manipulation, such as switching speed, switching direction, and applying voltages, were systematically investigated. This study provides basic understanding and electrical control of this unique phase boundary. [Preview Abstract] |
Wednesday, March 23, 2011 8:12AM - 8:24AM |
P33.00002: Oxygen ordering and electrochromism in Ca-doped BiFeO$_3 $ Jan Seidel, Weidong Luo, Phi Nguyen, Suresha Siriyara Jagannatha, Alan Lee, Sang-Yong Kim, Chan-Ho Yang, Stephen Pennycook, Sokrates Pantelides, Ramamoorthy Ramesh We show that calcium-doped bismuth ferrite thin films exhibit an electrochromic effect arising from an intrinsic mechanism due to redistribution of carriers, without the need for additional electrolytes that are needed in common electrochromic devices. The absorption change and coloration efficiency at the band edge are $4.8\times 10^6m^{-1}$and $190cm^2C^{-1}$, respectively, which are among the highest reported values for inorganic electrochromes. These experimental findings are supported by optical absorption calculations from first-principles theory, confirming the strong absorption change at the band edge. [Preview Abstract] |
Wednesday, March 23, 2011 8:24AM - 8:36AM |
P33.00003: Polarity Control of Ferroelectric BiFeO$_{3}$/Metal Junctions for Switchable Diode and Photovoltaic Devices Tae Won Noh, Daesu Lee, T.H. Kim, S.H. Baek, C.M. Folkman, C.B. Eom, J.-G. Yoon Ferroelectric materials possess spontaneous polarization which can be used to control numerous functionalities of the materials by switching the polarization or modifying domain structure with an electric field. One of emerging phenomena in ferroelectrics is the control of charge transport by switching the polarization. Although charge conduction ($i.e.$, leakage current) in ferroelectrics has been considered as a detrimental factor to practical applications, an interaction between conduction and ferroelectric polarization has recently attracted much attention as a route for novel functionalities. In this presentation, we will report on the ferroelectric control of charge conduction in BiFeO$_{3}$/metal junctions: the BiFeO$_{3}$/metal interfaces can have either blocking or non-blocking contacts according to the polarization direction of the BiFeO$_{3}$ films, allowing non-volatile control of diode-like conduction characteristics. The resulting rectifying and photovoltaic effects can be turned on and off, as well as be flipped in polarity, depending on the ferroelectric domain structures. [Preview Abstract] |
Wednesday, March 23, 2011 8:36AM - 8:48AM |
P33.00004: ABSTRACT WITHDRAWN |
Wednesday, March 23, 2011 8:48AM - 9:00AM |
P33.00005: Magnetic Order in single-crystal BiFeO$_{3}$ Mehmet Ramazanoglu, Sang-Wook Cheong, Valery Kiryukhin, William Ratcliff, S. Lee We report neutron scattering studies of the magnetic order in multiferroic Bismuth Ferrite (BiFeO$_{3}$). In ferroelectric monodomain single crystals, there are 3 equivalent magnetic cycloidal domains. The cycloid period slowly grows with increasing temperature, and the antiferromagnetic transition is 2nd order. The equivalent magnetic domain populations do not change with temperature, except in the close vicinity of the Neel temperature. No evidence for the spin-reorientation transitions proposed in previous Raman studies is found. The magnetic cycloid is slightly anharmonic for T=5 K. The anharmonicity is much smaller than previously reported in indirect NMR studies. At room temperature, a circular cycloid is observed. The observed anharmonicity provides important clues for understanding electromagnons in BiFeO$_{3}$. [Preview Abstract] |
Wednesday, March 23, 2011 9:00AM - 9:12AM |
P33.00006: Chemical substitution induced ferroelectric polarization rotation in BiFeO$_{3}$ thin films Ichiro Takeuchi, Daisuke Kan, Anbusathaiah Varatharajan The direction of the polarization vector in ferroelectric materials is an important parameter critical to a number of applications. Polarization orientation in ferroelectric thin films can be controlled by various approaches such as electric- field induced rotation and strain engineering using exotic substrates. We have performed systematic chemical substitution of rare earth cationic dopants, in particular Sm in the BiFeO$_ {3}$thin films, and found that the polarization vector rotates from the (111) to the (001) direction as a continuous function of the dopant concentration. This is accompanied by enhanced dielectric $\epsilon$$_{33}$ as well as piezoelectric coefficient d$_{33}$, and the maximum in d$_{33}$ (110 pm/V) is achieved at 14\% Sm. We will discuss the correlation between the polarization rotation, structural evolution and other properties as a function of chemical substitution. [Preview Abstract] |
Wednesday, March 23, 2011 9:12AM - 9:48AM |
P33.00007: Strain-stabilized phases of BiFeO3 and the role of first-principles calculations Invited Speaker: After many years of focused attention from the scientific community, the ferroelectric material BiFeO$_3$ (BFO) continues to be one of the most intriguing and technologically promising of the multifunctional ferroelectrics. Here I will discuss some of the recent developments on BFO thin films, including the metastable ``super-tetragonal'' phase achievable in epitaxial thin films. This strain-stabilized phase has been observed to coexist with a bulk-like phase, and reversible switching between the two has been demonstrated by acting on their ferroelectric polarizations with an external electric field. [Zeches {\em et al.}, Science 326, 977 (2009).] Related work finds a phase transition path of rhombohedral-to-monoclinic-to-tetragonal for epitaxially strained BFO, suggesting comparison to a compositional morphotropic phase boundary. I will discuss these results with an emphasis on the contributions from first-principles calculations, and provide context for understanding the calculated behaviors. [Preview Abstract] |
Wednesday, March 23, 2011 9:48AM - 10:00AM |
P33.00008: Experimental evidence of stress-induced R-M$_{A}$-M$_{C}$-T phase transition in BiFeO$_{3}$ films Hans Christen, Joong-Hee Nam, Charlee Bennett, Hyun-Sik Kim, Michael Biegalski Recent reports on epitaxial BiFeO$_{3}$ films show that the crystal structure changes from nearly rhombohedral (``R-like'') to nearly tetragonal (``T-like'') at strains exceeding $\approx $-4.5{\%}, with the ``T-like'' structure being characterized by a highly-enhanced $c/a$ ratio. While both the ``R-like'' and the ``T-like'' phases are monoclinic, our detailed x-ray diffraction results reveal a symmetry change from M$_{A}$ and M$_{C}$ type, respectively. Therefore, the ferroelectric polarization is confined to different (pseudocubic) planes in the two phases. By applying additional strain or by modifying the unit cell volume of the film by substituting Ba for Bi, the monoclinic distortion in the ``T-like'' M$_{C}$ phase is reduced, i.e. the system approaches a true tetragonal symmetry. Therefore, in going from bulk to highly-strained films, a phase sequence of rhombohedral(R)-to-monoclinic(``R-like'' M$_{A})$-to-monoclinic(``T-like'' M$_{C})$-to-tetragonal(T) is observed. This sequence is otherwise seen only near morphotropic phase boundaries in lead-based solid-solution perovskites (i.e. near a compositionally induced phase instability), where it can be controlled by electric field, temperature, or composition. Our results now show that this evolution can occur in a lead-free, stoichiometric material and can be induced by stress alone. [Preview Abstract] |
Wednesday, March 23, 2011 10:00AM - 10:12AM |
P33.00009: Strained BiFeO$_{3}$ Films: Rhombohedral-Orthorhombic and Rhombohedral-Tetragonal Phase Transitions. Part I: Phase-Field Simulations Guang Sheng, Jingxian Zhang, Zi-Kui Liu, Long-Qing Chen, Yulan Li In this study, the strain-temperature phase stability diagrams of (001) BiFeO$_{3}$ thin film were constructed using both thermodynamic analysis and phase-field simulations. The predicted diagram reveals a tetragonal to distorted rhombohedral phase boundary around 4.3{\%} compressive strain and rhombohedral to orthorhombic boundary at around 2{\%} tensile strain, both at room temperature. The predicted transition temperatures for rhombohedral-orthorhombic and rhombohedral-tetragonal transitions are in reasonable agreement with experimental observations. We will also discuss domain structure evolutions of BiFeO$_{3}$ thin films during the above two transitions from phase-field simulations. [Preview Abstract] |
Wednesday, March 23, 2011 10:12AM - 10:24AM |
P33.00010: Strained BiFeO3 Films: Rhombohedral-Orthorhombic and Rhombohedral-Tetragonal Phase Transitions. Part II: Film Growth by Molecular-Beam Epitaxy Carolina Adamo, R. Misra, A. Melville, C. Heikes, Q. He, Y. Chu, J. Lee, R. Haislmaier, S. Denev, V. Gopalan, R. Ramesh, P. Schiffer, D. Schlom Recently, Zeches et al.[1] reported the strain-temperature phase stability diagram of (001) BiFeO3 thin films. Depending on the strain and temperature the stable polymorph of BiFeO3 is predicted to be (monoclinically distorted) rhombohedral, tetragonal, or orthorhombic. To test these predictions commensurate BiFeO3 thin films were grown by adsorption-controlled reactive molecular-beam epitaxy on (110) YAlO3, (110) NdGaO3, (100) LSAT, (001) SrTiO3, (110) DyScO3, (110) TbScO3, (110) GdScO3, (110) SmScO3, (110) NdScO3, and (110) PrScO3 single crystalline substrates. The films span a biaxial strain range from -6.7\% to +1.4\%. Four-circle x-ray diffraction was used to determine the in-plane and out-of-plane lattice parameters. The rocking curve full widths at half maximum in omega of the films were nominally identical to the substrates on which they are grown and ranged from 11 arc sec (0.003 degrees) on (110) PrScO3 to 49 arc sec (0.014degrees) on (110) YAlO3. Magnetic data and second harmonic generation results will be presented. [1] R. J. Zeches, M. D. Rossell, J. X. Zhang, A. J. Hatt, Q. He, C.-H. Yang, A. Kumar, C. H. Wang, A. Melville, C. Adamo, G. Sheng, Y.-H. Chu, J. F. Ihlefeld, R. Erni, C. Ederer, V. Gopalan, L. Q. Chen, D. G. Schlom, N. A. Spaldin, L. W. Martin, and R. Ramesh, Science 326, 977 (2009). [Preview Abstract] |
Wednesday, March 23, 2011 10:24AM - 10:36AM |
P33.00011: Strained BiFeO$_3$ films: rhombohedral-orthorhombic and rhombohedral-tetragonal phase transitions. Part IV: ultraviolet Raman spectroscopy study Dmitri A. Tenne, A.K. Farrar, G. Molino, C. Heikes, C. Adamo, J.H. Lee, A. Melville, D.G. Schlom, G. Sheng, L.Q. Chen, Y.-H. Chu, Q. He, R. Ramesh Epitaxial BiFeO$_3$ films grown by molecular-beam epitaxy on substrates inducing different lattice-mismatch strain (YAlO$_3$, SrLaAlO$_4$, PrScO$_3$) have been studied by variable- temperature ultraviolet Raman spectroscopy. Temperature evolution of Raman spectra from BiFeO$_3$ films indicates the phase transitions from rhombohedral to tetragonal phase in compressively strained films on YAlO$_3$ and SrLaAlO$_4$ substrates. The films grown on PrScO3 substrates are subject to $\sim$1.3\% tensile strain, and undergo the transition from rhombohedral to orthorhombic phase at about 550-600 K. The temperature dependence of Raman intensities of certain characteristic peaks indicates the possibility of coexisting rhombohedral and orthorhombic phases in the temperature range 400-550 K. Raman results are consistent with the phase diagram calculated using the phase field model. [Preview Abstract] |
Wednesday, March 23, 2011 10:36AM - 10:48AM |
P33.00012: Emergence of 90$^\circ$ Domain Walls in Multiferroic BiFeO$_3$ Thin Film Jan-Chi Yang, Ying-Hao Chu, Chun-Yen Peng, Hsiang-Jung Chen, Li Chang, Qing He, Ramamoorthy Ramesh, Chao-Hui Yeh, Heng-Jui Liu, Sheng-Jie Liao, Po-Wen Chiu, Chih-Hung Lai Multiferroics have been a fascinating area for condensed materials research since these materials offer the exciting potential applications that taking advantages of multiple orders. Multiferroic BiFeO$_3$ (BFO) has played a key role in rejuvenating the field after a report of large ferroelectric polarization. Inside this material, domain walls (DWs) of BFO are of great interests. In recent study, room-temperature conductivity at ferroelectric DWs has been observed. In this work, through epitaxial strain, BFO thin films are grown on NdScO$_3$, which provide tensile strain on BFO films, and thus results in orthorhombic-like phase and corresponding periodic 90$^\circ$ DWs. X-ray reciprocal mapping and piezoresponse force microscopy has confirmed the orthorhombic-like and 90$^\circ$ DW structure. The transport behaviors of these natural formed 90$^\circ$ DWs as a function of temperatures and magnetic fields have been probed to understand their fundamental properties. In addition, exchange bias studies and X-ray magnetic dichroism spectromicroscopy have further revealed the magnetic properties in these DWs. Our results show that 90$^\circ$ DW in orthorhombic-like BFO possesses unusual electronic and magnetic behaviors, which are different from that in bulk and might be used for modern electronic devices and nanoelectronic. [Preview Abstract] |
Wednesday, March 23, 2011 10:48AM - 11:00AM |
P33.00013: ABSTRACT WITHDRAWN |
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