Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session X3: Topological Vortices in Magnets, Ferroelectrics, and Multiferroics |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Sang-Wook Cheong, Rutgers University Room: Ballroom A3 |
Thursday, March 24, 2011 2:30PM - 3:06PM |
X3.00001: Magnetic vortices: From a “hidden parameter” to novel switching modes Invited Speaker: This abstract not available. [Preview Abstract] |
Thursday, March 24, 2011 3:06PM - 3:42PM |
X3.00002: Skyrmion Lattices in Chiral Magnets Invited Speaker: Skyrmions are topologically stable field configurations with particle-like properties. Using neutron scattering and measurements of the Hall effect we identified the formation of two-dimensional lattices of skyrmion lines, a new form of magnetic order, in metallic and semiconducting B20 compounds, namely MnSi [1,2], Mn$_{1-x}$Co$_x$Si [3], Mn$_{1-x}$Fe$_x$Si [3] and Fe$_{1-x}$Co$_x$Si [4]. The existence of individual skyrmions and skyrmion lattices has recently been confirmed by Lorentz force microscopy for Fe$_{1-x}$Co$_x$Si ($x=0.5$) [5]. The skyrmion lattices in chiral magnets share remarkable similarities with vortex lattices in type II superconductors -- they may be understood as vortex lattices of transverse spin supercurrents exhibiting domain formation and complex morphologies. Our studies establish magnetic materials lacking inversion symmetry as an arena for new forms of order composed of topologically stable spin configurations. \\[4pt] [1] S. M{\"u}hlbauer, et al. Science \textbf{323}, 915 (2009).\\[0pt] [2] A. Neubauer, et al. Phys. Rev. Lett. \textbf{102}, 186602 (2009).\\[0pt] [3] C. Pfleiderer, et al. J. Phys. Cond. Matter \textbf{22}, 164207 (2010).\\[0pt] [4] W. M{\"u}nzer, et al. Phys. Rev. B (R) \textbf{81}, (2010).\\[0pt] [5] X. Z. Yu, et al. Nature \textbf{465}, 901 (2010); C. Pfleiderer, A. Rosch, Nature (N\&V) \textbf{465}, 880 (2010). [Preview Abstract] |
Thursday, March 24, 2011 3:42PM - 4:18PM |
X3.00003: Skyrmion crystal and topological Hall effect in B20-type transition-metal compounds Invited Speaker: Topological objects in solids such as domain walls and vortices have been attracting much attention for long. Among them the spin texture called skyrmion is an unusual topological object, in which the spins point in all the directions wrapping a sphere. The skyrmion hosts finite spin chirality, and therefore is anticipated to induce novel electromagnetic phenomena such as topological Hall effect. In B20-type transition metal compounds MnSi and Fe$_{1-x}$Co$_x$Si, the crystallization of skyrmions was observed by the neutron diffraction studies.\footnote{S. M\"{u}hlbauer {\it et al.,} Science {\bf 323,} 915 (2009).}$^,$\footnote{W. M\"{u}nzer {\it et al.,} Phys. Rev. B {\bf 81,} 041203 (2010).} Recently, we have observed the real-space images of skyrmion crystal in thin films of related compounds (Fe$_{0.5} $Co$_{0.5}$Si and FeGe) using Lorentz transmission electron spectroscopy.\footnote{X. Z. Yu, {\it et al.}, Nature, {\bf 465,} 901 (2010).}$^,$\footnote{X. Z. Yu, {\it et al.,} Nature material, {\it inpress}.} We have observed the hexagonal arrangement of skyrmions including the topological defects (chiral domains and dislocations) under the magnetic field normal to the films, and found that the two dimensional skyrmion crystal phase is fairly stabilized by the thin film form of the samples. We have also studied the topological Hall effect caused by the spin chirality of the skyrmion crystal in a related material MnGe. In terms of the Hall measurement, they have shown the real space nature of the fictitious magnetic field caused by the magnetic configuration of the skyrmion crystal, in contrast with the momentum-space fictitious field in another spin chirality system, Nd$_2$Mo$_2$O$_7$.\footnote{Y. Taguchi {\it et al.,} Science {\bf 291,} 2573 (2001).} This work was done in collaboration with X. Z. Yu, N. Kanazawa, J. H. Park, J. H. Han, K. Kimoto, W. Z. Zhang, S. Ishiwata, Y. Matsui, N. Nagaosa, and Y. Tokura. [Preview Abstract] |
Thursday, March 24, 2011 4:18PM - 4:54PM |
X3.00004: Multiferroic vortices in hexagonal manganites Invited Speaker: Hexagonal rare earth manganites (\textit{RE}MnO$_3$) show a unique improper ferroelectricity induced by structural trimerization. Extensive research on these systems has been carried out due to its potential application in memory and the intriguing multiferroicity (coexistence of ferroelectricity and antiferromagnetism). However, the true relationship between ferroelectric domains and structural domains has never been revealed. Using transmission electron microscopy (TEM) and conductive atomic force microscopy (cAFM), we observed an intriguing conductive ``cloverleaf'' pattern of six domains emerging from one point, all distinctly characterized by polarization orientation and structural antiphase relationships in hexagonal manganites.\footnote{T. Choi, et al, ``Insulating interlocked ferroelectric and structural antiphase domain walls in multiferroic YMnO$_3$'' Nature Materials, \textbf{9}, 253-258 (2010).} The nanoscale electric conduction between a sharp tip and the surface is intrinsically modulated by the ferroelectric polarization.\footnote{W. Wu, et al, ``Polarization-Modulated Rectification at Ferroelectric Surfaces'' Phys. Rev. Lett., \textbf{104}, 217601 (2010).} The cloverleaf defects are structural vortices where the phase angle goes successively through all six phases.\footnote{M. Mostovoy, ``a whirlwind of opportunities,'' Nature Materials, \textbf{9}, 188-190 (2010).} In addition, we discovered that the ferroelectric domain walls and structural antiphase boundaries are mutually locked. Correlated with previous observation of coupled ferroelectric and antiferromagnetic domain walls,\footnote{M. Fiebig, et al, ``Observation of coupled magnetic and electric domains,'' Nature, \textbf{419}, 818 (2002).} our results suggest that these cloverleaf defects are indeed multiferroic vortices. These fascinating results reveal the rich physics of the hexagonal system with a semiconducting bandgap where structural trimerization, ferroelectricity, magnetism and charge conduction are intricately coupled. [Preview Abstract] |
Thursday, March 24, 2011 4:54PM - 5:30PM |
X3.00005: Ferroelectric vortices from atomistic simulations Invited Speaker: In 2004, the use of a first-principles-based effective Hamiltonian [1] led to the prediction of a novel structure in zero-dimensional ferroelectrics, in which the electric dipoles organize themselves to form a vortex [2]. Such structure exhibits the so-called spontaneous toroidal moment, rather than the spontaneous polarization, as its order parameter [2]. Subsequently, various original phenomena, all related to vortices, were predicted in ferroelectric nanostructures. Examples of such phenomena are: (i) the existence of a new order parameter, denoted as the hypertoroidal moment, that is associated with many complex dipolar structures (such as double-vortex states) [3]; (ii) the possible control of single and double vortex states by electric fields, via the formation of original intermediate states [4-8]; (iii) the discovery of a new class of quantum materials (denoted as incipient ferrotoroidics), for which zero-point vibrations wash out the vortex state and yield a complex local structure [9]; (iv) the existence of chiral patterns of oxygen octahedral tiltings that originate from the coupling of these tiltings with the ferroelectric vortices [10]. The purpose of this talk is to discuss some of these striking phenomena, as well as, to reveal others (if time allows). These studies are done in collaboration with A.R. Akbarzadeh, H. Fu, I. Kornev, I. Naumov, I. Ponomareva, S. Prosandeev, Wei Ren and D. Sichuga. \\[4pt] [1] L. Bellaiche, A. Garcia and D. Vanderbilt, Phys. Rev. Lett. 84, 5427 (2000). \\[0pt] [2] Ivan I. Naumov, L. Bellaiche and Huaxiang Fu, Nature (London) 432, 737 (2004). \\[0pt] [3] S. Prosandeev and L. Bellaiche, Phys. Rev. B 77, 060101(R) (2008). \\[0pt] [4] S. Prosandeev, I. Ponomareva, I. Kornev, I. Naumov and L. Bellaiche, Phys. Rev. Lett. 96, 237601 (2006). \\[0pt] [5] I. Naumov and H. Fu, Phys. Rev. Lett. 98, 077603 (2007). \\[0pt] [6] S. Prosandeev and L. Bellaiche, Phys. Rev. Lett. 101, 097203 (2008). \\[0pt] [7] S. Prosandeev, I. Ponomareva, I. Kornev, and L. Bellaiche, Phys. Rev. Lett. 100, 047201 (2008). \\[0pt] [8] I. Naumov and H. Fu, Phys. Rev. Lett. 101, 197601 (2008). \\[0pt] [9] S. Prosandeev, A. R. Akbarzadeh and L. Bellaiche, Phys. Rev. Lett. 102, 257601(2009). \\[0pt] [10] David Sichuga, Wei Ren, Sergey Prosandeev, and L. Bellaiche, Phys. Rev. Lett. 104, 207603 (2010). [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. |
© 2025 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