Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session R30: Properties of Multiferroic MaterialsFocus
|
Hide Abstracts |
Sponsoring Units: DMP DCMP Chair: Sergey Artyukhin, Rutgers University Room: 329 |
Thursday, March 17, 2016 8:00AM - 8:36AM |
R30.00001: Large-amplitude spin dynamics driven by a THz pulse in resonance with an electromagnon Invited Speaker: Steven Johnson With femtosecond time resolution, x-ray diffraction offers unique capabilities to observe directly the dynamics of long range order. When the x-ray energy is tuned near a core-level transition is is possible in many systems to selectively study the dynamics of long-range order of valence properties such as orbital ordering or magnetic spin. Here I discuss show how resonantly enhanced magnetic scattering can be used to quantitatively measure the character and magnitude of spin motion in a coherent electromagnon in TbMnO$_3$ driven by a THz frequency electromagnetic field. We observe a $4^\circ$ rotation of the antiferromagnetically ordered spin spiral plane, a result consistent with a previously published model that suggests this may be a viable route for ultrafast domain switching in multiferroics. [Preview Abstract] |
Thursday, March 17, 2016 8:36AM - 8:48AM |
R30.00002: Terahertz excitations of spin-orbital ground state in multiferroic Sr$_2$FeSi$_2$O$_7$ Thuc Mai, C. Svoboda, E.V. Jasper, M.T. Warren, J. Brangham, S-W. Cheong, T-H. Hwan, R. Vald\'{e}s Aguilar We studied the elementary excitations in Sr$_2$FeSi$_2$O$_7$, a novel multiferroic material, using time domain terahertz spectroscopy. We found 3 absorption modes above the N\'{e}el temperature. These modes can be described as optical transitions between the Fe$^{2+}$ 3d$^6$ energy levels, that are split by the compressive tetrahedral crystal field and spin orbit coupling. The excitations from the singlet spin-orbital ground state to the upper doublets are both magnetic and electric dipole active. We explored the behavior of these transitions at temperatures below T$_{N\'{e}el}$, and as a function of external magnetic field, applied along different crystalline axes. [Preview Abstract] |
Thursday, March 17, 2016 8:48AM - 9:00AM |
R30.00003: Non-reciprocal directional dichroism in the AFM phase of BiFeO$_3$ at THz frequencies Urmas Nagel, T. R\~o\~om, D. Farkas, D. Szaller, S. Bord\'acs, I. K\'ezsm\'arki, H. Engelkamp, Y. Ozaki, Y. Tomiaki, T. Ito, Randy S. Fishman We did THz absorption spectroscopy of BiFeO$_3$ single crystals in the AFM phase, where the spin cycloid is destroyed in magnetic fields between 18\,T and 32\,T in Voigt geometry at 1.6\,K. If $\mathbf{B}_0 \parallel [1\bar{1}0]$, we see strong directional dichroism (DD) of absorption of the magnon mode with light propagating along the direction of the ferroelectric polarization $\mathbf{k} \parallel \mathbf{P} \parallel [111]$ and $\mathbf{e}^\omega \parallel [1\bar{1}0]$, $\mathbf{b}^\omega \parallel [\bar{1}\bar{1}2]$. The sign of DD can be reversed (\i) by reversing the direction of $\mathbf{B}_0$ or (ii) by flipping the sample, thus reversing the propagation direction of light. The observed effect is caused by the strong magneto-electric coupling in the collinear AFM phase. [Preview Abstract] |
Thursday, March 17, 2016 9:00AM - 9:12AM |
R30.00004: Ultrafast Anisotropic Optical Response and Coherent Acoustic Phonon Generation in Polycrystalline BaTiO3-BiFeO3 B. A. Magill, G. A. Khodaparast, M. Gyu Kang, Y. Zhou, H-C Song, S. Priya Ultrafast optical spectroscopy can provide insight into fundamental microscopic interactions, dynamics and the coupling of several degrees of freedom. Pump/ probe studies can reveal the answer to questions like “What are the achievable switching speeds in multiferroics?”, “What is the influence of the crystallographic orientation and domain states on the available switching states?”, and “What is the effect of the hetrostructure on promoting the coupling between the varying field excitations?”. In this presentation, we report on two color (400/800nm) ultrafast pump-probe differential reflectance spectroscopy of $BiFeO_{3}-BaTiO_{3}$ structures. The $(001)-BiFeO3-BaTiO3$ thin films were prepared using pulsed laser deposition on vicinal $SrTiO_{3}$ substrates using LSMO bottom electrodes. Crystal orientation and topography were analyzed by x-ray diffraction and atomic force microscopy. The films were found to exhibit perovskite phase and in our study, we introduce the first observation of photoexcited strain waves, with the frequencies in the GHz range. [Preview Abstract] |
Thursday, March 17, 2016 9:12AM - 9:24AM |
R30.00005: Optical diode effect at THz frequencies of spin-wave excitations in the room-temperature multiferroic BiFeO$_3$ Toomas R{\~o\~o}m, U. Nagel, S. Bord\'acs, I. K\'ezsm\'arki, H.T. Yi, S.-W. Cheong, J. H. Lee, R.S. Fishman We studied the unidirectional transmission of THz radiation in BiFeO$_3$ crystals, the unique multiferroic compound offering a real potential for room-temperature applications. We found that the optical magnetoelectric effect generated by spin waves in BiFeO$_3$ is robust enough to cause considerable nonreciprocal directional dichroism in the GHz-THz range even at room temperature. The optical magnetoelectric effect in BiFeO$_3$ is dominated by two types of spin-current induced polarizations, while the exchange-striction and single-ion polarization terms do not significantly contribute to it. Our work demonstrates that the nonreciprocal directional dichroism spectra and their theoretical analysis provide microscopic model of the magnetoelectric couplings in multiferroic materials. [Preview Abstract] |
Thursday, March 17, 2016 9:24AM - 9:36AM |
R30.00006: Magnetoelectric coupling in hexagonal LuFeO3 thin films Hao Liu The magnetic and polar properties of single-crystalline hexagonal LuFeO3 films have been studied. Both theoretical and experimental approaches indicated the coexisting of multiple ferroic orders. The spontaneous electric polarization is associated with a structural change, which also influences the magnetic properties, predicting a strong magnetoelectric coupling in these films. To investigate the magnetoelectric coupling, the micro capacitance structures were fabricated by photolithography combined with Ar ion beam etching method. The capacitance vs voltage curves show significant magnetic field effect, indicating strong magnetoelectric coupling in this system. [Preview Abstract] |
Thursday, March 17, 2016 9:36AM - 9:48AM |
R30.00007: Temperature Dependent Atomic and Electronic Structure of LuFe2O4 Sizhan Liu, Han Zhang, Sanjit Ghose, Thomas Emge, Daniel Kaplan, Cherno Jaye, Daniel Fisher, Sang-Wook Cheong, Trevor Tyson Structural measurements on multiple length scales have been conducted over a broad range of temperatures. These measurements have been complemented by optical and thermal measurements. The nature of the observed local atomic and electronic structural changes will be discussed and compared with previous work. This work is supported by DOE Grant DE-FG02-07ER46402. [Preview Abstract] |
Thursday, March 17, 2016 9:48AM - 10:00AM |
R30.00008: Structure of Multiferroic RAl3(BO3)4 and RFe3(BO3)4 in the Region of High Electric Polarization Han Zhang, Tian Yu, Zhiqiang Chen, Christie Nelson, Leonard Bezmaternykh, Yu-sheng Chen, Milinda Abeykoon, Trevor Tyson The multiferroic system RAl$_{\mathrm{3}}$(BO$_{\mathrm{3}})_{\mathrm{4}}$ is known to exhibit a strong coupling of magnetic field to the electrical polarization at low temperature (below \textasciitilde 100 K). A giant magnetoelectric effect was found in this$_{\mathrm{\thinspace }}$system. Recent work by us (PRB B \textbf{92} 104108) reveals evidence for changes in the local structure at low temperature. In this work we explore the structural changes using single crystal diffraction and other structural probes. Comparisons between the Fe and Al based systems will be made. This work is supported by DOE Grant DE-FG02-07ER46402. [Preview Abstract] |
Thursday, March 17, 2016 10:00AM - 10:12AM |
R30.00009: Optical and Electro-Optical Properties of RFe$_{\mathrm{2}}$O$_{\mathrm{4}}$ (R $=$ Y and Yb) Thin Films Ram Rai, Michelle Pascolini, Joshua Hinz We present optical, and electro-optical properties of RFe$_{\mathrm{2}}$O$_{\mathrm{4\thinspace }}$(R $=$ Y and Yb) thin films deposited on sapphire and YSZ substrates by reactive electron-beam deposition. In order to investigate the electronic transitions and optical properties, we measured transmittance and reflectance of the RFe$_{\mathrm{2}}$O$_{\mathrm{4\thinspace }}$thin films in the 1 -- 6 eV photon energy range and at temperatures from 10 to 400 K. The optical spectra of RFe$_{\mathrm{2}}$O$_{\mathrm{4\thinspace }}$show several electronic peaks arising from Fe$^{\mathrm{2+}} \quad d $to $d $on-site and O 2$p $to Fe 3$d$, Y 4$d$ and Y 5$s$ (Yb 5$d$ and 6$s)$ charge-transfer transitions. Interestingly, the electronic excitations display strong temperature dependence with an anomaly between 170 K and 190 K, indicating a structural distortion. Moreover, the electro-optical effects up to \textpm 10 {\%} have been observed in the RFe$_{\mathrm{2}}$O$_{\mathrm{4\thinspace }}$thin films at 10 K for applied electric fields below 1 kV/cm. These electro-optical effects mostly occur between the photon energy of 1 and 3 eV, vary almost linearly with applied fields, and the effects disappear above 150 K. We will discuss the driving mechanism for the observed electro-optical effects of these compounds. [Preview Abstract] |
Thursday, March 17, 2016 10:12AM - 10:24AM |
R30.00010: Magnetically induced ferroelectricity in single crystalline ferrimagnet, Mn$_2$Mo$_3$O$_8$ Shalinee Chikara, John Singleton, Bin Gao, Yazhong Wang, Sang-Wook Cheong, Vivien Zapf We present magnetization and electric polarization results on multiferroic ferrimagnet molybdate system, Mn$_2$Mo$_3$O$_8$ in pulsed magnetic fields. Mn$_2$Mo$_3$O$_8$, also known as the mineral isiemite crystallizes in a hexagonal P6${_3}mc$ space group. The magnetism is attributed to the Mn ions whereas the Mo is diamagnetic. The Mo and Mn atoms are stacked alternately along \boldface{c}-axis. The Mn ions form a hexagonal lattice and occur in octahedral and tetragonal coordination. The spins on two different Mn sites give rise to ferrimagnetism. The system orders at about 42 K accompanied by a lambda like anomaly in heat capacity. Mn$_2$Mo$_3$O$_8$ shows anisotropic magnetization with a change in slope at 40 K signaling possibly an AFM to ferrimagnet ordering. We observe magnetic field induced electric polarization in our preliminary results and an anomaly at 40 K corresponding to T$_N$. [Preview Abstract] |
Thursday, March 17, 2016 10:24AM - 10:36AM |
R30.00011: Temperature Dependent Structure of BiFeO$_{3}$: Probing For Spin Lattice Correlations Trevor Tyson, Tian Yu, Han Zhang, Milinda Abeykoon The local structure of BiFeO3 has been measured over a broad range of temperatures and in magnetic fields. This detailed study explores the nature of the coupling of magnetism and with the lattice on crossing magnetic transitions. Estimates on the structural changes are given. This work is supported by DOE Grant DE-FG02-07ER46402. [Preview Abstract] |
Thursday, March 17, 2016 10:36AM - 10:48AM |
R30.00012: Lattice and magnetic excitations in NdFe$_3$(BO$_3$)$_4$ Ricardo Lobo We measured the temperature dependent polarized infrared spectra of multiferroic NdFe$_3$(BO$_3$)$_4$. The spectra is mostly temperature independent except for the lowest energy phonon in the hexagonal plane. This phonon splits into two at around 60 K, a temperature sensibly larger than the system N\'eel temperature of 31 K. X-ray scattering indicates that the lattice parameters have an anomaly at the same temperature that the phonon splits. Using inelastic neutron scattering we looked for magnetic excitations that could explain be coupled to phonons. Momentum and energy dispersion curves around the magnetic Bragg peaks show magnetic excitations at energies comparable to the split phonon. We will discuss these results in terms of magnetic fluctuations and activation of Brillouin zone boundary modes. [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