Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session S41: Focus Session: Hexagonal Manganites and Ferrites and Perovskite Stannates |
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Sponsoring Units: DMP DCOMP Chair: Hiroyuki Takenaka, University of Pennsylvania Room: Mile High Ballroom 3C |
Thursday, March 6, 2014 8:00AM - 8:12AM |
S41.00001: Temperature Dependent Properties of E-Phase Perovskite ScMnO$_{3}$ Haiyan Chen, Tian Yu, Trevor Tyson, A.M. Milinda Abeykoon, Keun Ahn, Yusheng Chen Perovskite~E-type ScMnO$_{3}$ was synthesized under high temperature and pressure. Combined local and long range structural measurements were conducted using XAFS, PDF and single crystal XRD methods. The local structure of different ion sites was explored with x-ray absorption spectroscopy in low temperature. The detailed changes in structure on crossing into the magnetically ordered region are explored and compared with DFT electric polarization calculations. The accuracy of DFT models to assess the electric polarization components (structural and electronic) is discussed. This work is supported by DOE Grant DE-FG02-07ER46402. [Preview Abstract] |
Thursday, March 6, 2014 8:12AM - 8:24AM |
S41.00002: Local Structural Changes at Low Temperature in Hexagonal InMnO$_{3}$ Tian Yu, Peng Gao, Tao Wu, Trevor Tyson, Xingguo Hong, Yusheng Chen, Roger Lalancette Single crystal structural, electric polarization and heat capacity measurements on the hexagonal InMnO$_{3}$ have revealed that this small R ion material is ferroelectric at room temperature. In addition, temperature dependent electrical polarization measurements down to $\sim$ 10K were conducted. In parallel, structural measurements on single crystal and powders were carried out. Evidence is found for local distortions which are strongly enhanced as temperature decreases. The connection between the structural changes and the bulk polarization is explored. Strong spin lattice coupling is evidenced in two temperature regions (near $\sim$ 120 and 40 K). This work is supported by DOE Grant DE-FG02-07ER46402. [Preview Abstract] |
Thursday, March 6, 2014 8:24AM - 8:36AM |
S41.00003: $Z_2\times Z_3$ vortex density in hexagonal manganites and the Kibble-Zurek mechanism Xueyun Wang, Sang-Wook Cheong Hexagonal $REMnO_3 (RE=Ho, Er, Tm, Yb, Lu)$ is an improper ferroelectric where the size mismatch between RE layers and Mn-O layers induces a simultaneous ferroelectric-trimerization structural phase transition. Six types of ferroelectric-trimerization domains form the so-called $Z_2\times Z_3$ vortices. We have carefully examined how the $Z_2\times Z_3$ vortex density changes with the cooling rate across the transition temperature, and compared the result with the so-called Kibble-Zurek mechanism, which is relevant to the formation of cosmological defects such as cosmological strings. [Preview Abstract] |
Thursday, March 6, 2014 8:36AM - 9:12AM |
S41.00004: Structural domain walls in polar hexagonal manganites Invited Speaker: Yu Kumagai The domain structure in the multiferroic hexagonal manganites is currently intensely investigated, motivated by the observation of intriguing sixfold topological defects at their meeting points [Choi, T. et al,. Nature Mater. 9, 253 (2010).] and nanoscale electrical conductivity at the domain walls [Wu, W. et al., Phys. Rev. Lett. 108, 077203 (2012).; Meier, D. et al., Nature Mater. 11, 284 (2012).], as well as reports of coupling between ferroelectricity, magnetism and structural antiphase domains [Geng, Y. et al., Nano Lett. 12, 6055 (2012).]. The detailed structure of the domain walls, as well as the origin of such couplings, however, was previously not fully understood. In the present study, we have used first-principles density functional theory to calculate the structure and properties of the low-energy structural domain walls in the hexagonal manganites [Kumagai, Y. and Spaldin, N. A., Nature Commun. 4, 1540 (2013).]. We find that the lowest energy domain walls are atomically sharp, with \textbraceleft 210\textbraceright orientation, explaining the orientation of recently observed stripe domains and suggesting their topological protection [Chae, S. C. et al., Phys. Rev. Lett. 108, 167603 (2012).]. We also explain why ferroelectric domain walls are always simultaneously antiphase walls, propose a mechanism for ferroelectric switching through domain-wall motion, and suggest an atomistic structure for the cores of the sixfold topological defects. [Preview Abstract] |
Thursday, March 6, 2014 9:12AM - 9:24AM |
S41.00005: Crystal Structure and Physical Properties of Multiferroic TmMnO$_{3}$ single crystals Yuqin Zhang, Tian Yu, Trevor Tyson We present here single crystal diffraction and local structure results of hexagonal and orthorhombic TmMnO$_{3}$ single crystals. Combined with specific heat and electric polarization properties across the N\'{e}el temperature, we further explore the close correlation between ferroelectric behavior at low temperature and local and long range structure change in these two different crystal structures. This work is supported by DOE Grants DE-FG02-07ER46402 (NJIT). [Preview Abstract] |
Thursday, March 6, 2014 9:24AM - 9:36AM |
S41.00006: Fluctuation-enhanced magnetoelectric effect in hexagonal manganites Yanan Geng, Hena Das, A.L. Wysocki, Xueyun Wang, S-W. Cheong, M. Mostovoy, Craig J. Fennie, Weida Wu Intensive studies have been focused on enhancing magnetoelectric (ME) effect ever since Dzyaloshinskii and Astrov's seminal works on linear ME effect in Cr$_{\mathrm{2}}$O$_{\mathrm{3}}$. The coupling between the magnetic and electric dipoles in multiferroic and magnetoelectric materials holds promise of conceptually new electronic devices. Herein, we report on the Magnetoelectric Force Microscopy (MeFM) studies on the multiferroic hexagonal manganites. The direct visualization of the ME domains with topological vortex pattern provides compelling evidence for the mechanism of lattice-mediated ME response. Furthermore, our MeFM results reveal a diverging magnetoelectric effect in the vicinity of a tri-critical point, suggesting a possibility to enhance ME effects by harnessing critical fluctuations. [Preview Abstract] |
Thursday, March 6, 2014 9:36AM - 9:48AM |
S41.00007: Mode Coupling between the Nonpolar K$_{3}$ and Polar $\Gamma _{2}^{-}$ Phonons as the Ferroelectricity Origin of Multiferroic h-LuMnO$_{3}$ Seungwoo Song, Seungyang Heo, Hyun Myung Jang LuMnO$_{3}$ is expected to show the highest stability towards the hexagonal phase among 15 different lanthanide-based manganites. Currently, the most puzzling problem associated with the hexagonal LuMnO$_{3}$ (h-LMO) is the observed large temperature-gap between the structural phase transition to the polar P6$_{3}$cm phase at $\sim$ 1290 K and the emergence of the spontaneous polarization at a substantially reduced temperature, $\sim$ 750 K. This anomalous temperature-gap has also been observed in h-YMnO$_{3}$. To resolve this puzzling issue, we have carried out density-functional theory calculations and found that the structural phase transition to the polar P6$_{3}$ cm phase from the nonpolar P63/mmc phase is mediated by the freezing-in of the zone-boundary K$_{3}$ phonon in h-LMO. However, the spontaneous ferroelectric polarization does not appear until the amplitude of K$_{3}$ phonon becomes a certain critical value above which the coupling of the polar $\Gamma_{2}^{-}$ mode with the nonpolar K$_{3}$ mode is practically turned on. This mode-coupling-induced polarization, thus, elucidates the above puzzle. [Preview Abstract] |
Thursday, March 6, 2014 9:48AM - 10:00AM |
S41.00008: ABSTRACT WITHDRAWN |
Thursday, March 6, 2014 10:00AM - 10:12AM |
S41.00009: Large photoconductivity in transparent perovskite semiconductor BaSnO3 Jisung Park, Useong Kim, Hoonmin Kim, Kookrin Char Photoconductivity of perovskite oxide such as SrTiO3 (STO) has been intensively studied because of its large potential for applications such as UV detector and optical devices. We have measured the photoconductivity of transparent perovskite semiconductor BaSnO3 (BSO) which has started to attract a large attention due to its high electron mobility and thermal stability. Measured photoconductivity of BSO is 1000 times higher than that of STO, although BSO and STO have the same perovskite structure and similar band gap. Epitaxial thin films of BSO and STO were made by pulsed laser deposition on a large bandgap substrates such as sapphire and MgO. The spectral responses measured by a monochromator have peaks around the band gap of each film, which is a clear evidence that electron-hole pair generation is the main mechanism of photoconductivity of both materials. The high mobility of BSO, which is two orders of magnitude larger than that of STO at room temperature, should be partially responsible for the higher photoconductivity. In addition, the small difference between the direct gap and indirect gap of BSO may make band to band transition easier. The results suggest that BSO can be used as more effective UV detector and optical devices than STO. [Preview Abstract] |
Thursday, March 6, 2014 10:12AM - 10:24AM |
S41.00010: ABSTRACT WITHDRAWN |
Thursday, March 6, 2014 10:24AM - 10:36AM |
S41.00011: Field Effect in transparent perovskite semiconductor BaSnO3 Useong Kim, Chulkwon Kim, Chanjong Ju, Woongjae Lee, Kee Hoon Kim, Kookrin Char A field effect transistor made entirely of perovskite materials has great potentials since it can be easily integrated in future devices controlling various properties. Recently, perovskite La-doped BaSnO$_{3}$ (BLSO) were reported to possess high electron mobility and thermal stability. We fabricated a field effect transistor structure on SrTiO$_{3}$ substrates using BLSO as a channel layer and lattice-matched LaInO$_{3}$(LIO) as a gate dielectric. We have measured the dielectric properties of the epitaxial LIO, such as the dielectric constant and the breakdown field. Using this gate oxide, we obtained the conductivity modulation by a factor of 5 in the channel with the electric field of 1.3 MV/cm. The magnitude of the field effect was found to be consistent with the materials parameters of BLSO and LIO. During the modulation process, the leakage current between the gate and channel was about 4 orders of magnitude lower than the channel current. The field effect mobility in the channel was calculated as 13 cm$^{2}$/Vs, which is comparable to the mobility of BLSO films in our previous study and indicates that the conductivity modulation was caused by modulation of carriers. Our field effect results suggest that the BLSO/LIO interface seems ideal, devoid of any charge trap or extra scattering. [Preview Abstract] |
Thursday, March 6, 2014 10:36AM - 10:48AM |
S41.00012: pn junctions based on a single transparent perovskite semiconductor BaSnO3 Hoon Min Kim, Useong Kim, Chulkwon Park, Hyukwoo Kwon, Woongjae Lee, Tai Hoon Kim, Kee Hoon Kim, Kookrin Char Successful p doping of transparent oxide semiconductor will further increase its potential, especially in the area of optoelectronic applications. We will report our efforts to dope the BaSnO3 (BSO) with K by pulsed laser deposition. Although the K doped BSO exhibits rather high resistivity at room temperature, its conductivity increases dramatically at higher temperatures. Furthermore, the conductivity decreases when a small amount of oxygen was removed from the film, consistent with the behavior of p type doped oxides. We have fabricated pn junctions by using K doped BSO as a p type and La doped BSO as an n type material. I\textunderscore V characteristics of these devices show the typical rectifying behavior of pn junctions. We will present the analysis of the junction properties from the temperature dependent measurement of their electrical properties, which shows that the I\textunderscore V characteristics are consistent with the material parameters such as the carrier concentration, the mobility, and the bandgap. Our demonstration of pn junctions based on a single transparent perovskite semiconductor further enhances the potential of BSO system with high mobility and stability. [Preview Abstract] |
Thursday, March 6, 2014 10:48AM - 11:00AM |
S41.00013: Structural, Magnetic and Transport Study on SrSn$_{\mathrm{1-x}}$Ru$_{\mathrm{x}}$O$_{3}$ system HyukWoo Kwon, Juyeon Shin, Kookrin Char SrSnO$_{3}$ is a diamagnetic material with a wide band gap. A theoretical calculation predicts that small Ru doped SrSnO$_{3}$ can be a dilute magnetic semiconductor (DMS) material. We have epitaxially grown the SrSn$_{\mathrm{1-x}}$Ru$_{\mathrm{x}}$O$_{3}$ (0 $\le $ x $\le $ 0.3) system by the pulsed laser deposition X-ray diffraction measurements show that films maintain a single phase over the doping range and lattice constants of the system decrease monotonously as the doping increases Transport measurements show that the films are semiconducting and their resistivities dramatically decrease as the Ru doping increases. On the other hand, Hall measurement data shows that the conduction of this system is mediated by hole carriers, which is closely related to the p-type conduction in SrRuO$_{3}$, and its corresponding mobility values vary from 0.1 $\sim$ 30 cm$^{2}$/V$\cdot$s, depending on the doping rate. Magnetic measurement data will be presented to investigate its ferromagnetism due to the doped Ru 4d character. In light of the electrical and magnetic property of this system, SrSn$_{\mathrm{1-x}}$Ru$_{\mathrm{x}}$O$_{3}$ system can be a promising material system for the field of spintronics and optoelectronics. [Preview Abstract] |
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