Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session W28: Focus Session: Device Applications of Multiferroic Structures |
Hide Abstracts |
Sponsoring Units: FIAP DMP Chair: Ichiro Takeuchi, University of Maryland Room: 330 |
Thursday, March 19, 2009 11:15AM - 11:51AM |
W28.00001: Multiferroic Microwave and Millimeter Wave Devices Invited Speaker: Layered composites of ferrites and ferroelectrics are magneto-electric (ME) multiferroics and are of interest for studies on the physics of ME interactions and for novel signal processing devices. There are two types of interactions. (i) \textit{ME coupling in bound ferrite-piezoelectrics:} An electric field E applied to the composite produces a mechanical deformation in the piezoelectric phase that in turn is coupled to the ferrite, resulting in a shift in the ferromagnetic resonance field. The strength of the interactions is measured from the FMR shifts. (ii) \textit{ME interactions in unbound ferrite-ferroelectrics}: This is a proximity effect in which hybrid spin-electromagnetic waves are formed. An electric field applied to the ferroelectric will result in a change in the permittivity and a shift in the hybrid modes. We performed studies on the nature of ME interactions at 1-110 GHz in bilayers of epitaxial yttrium iron garnet (YIG) films, single crystal spinel ferrites or hexagonal ferrites and single crystal lead magnesium niobate-lead titanate (PMN-PT) or polycrystalline lead zirconium titanate (PZT). A stripline structure or a cavity resonator was used. Electric fields effects were investigated on magnetostatic waves, uniform precession modes or hybrid modes in the ferrite. We found evidence for strong microwave ME coupling. The coupling strength has been found to be dependent on magnetic field orientation, the nature of piezoelectric coupling and volume for both phases [1]. The high frequency ME effect is of importance for dual electric and magnetic field tunable ferrite-ferroelectric devices. We will discuss the design and characterization of ME resonators, phase shifters, delay lines and filters [2]. The work is supported by grants from the Army Research Office and the office of Naval Research. \\[4pt] [1] ``Multiferroic magnetoelectric composites: Historical perspective, status, and future direction,'' Ce-Wen Nan, M. I. Bichurin, S. Dong, D. Viehland, and G. Srinivasan, J. Appl. Phys.\textbf{ 103}, 031101 (2008). \\[0pt] [2] ``Magnetoelectric interactions in a ferromagnetic-piezoelectric layered structures: Phenomena and devices,'' M. I. Bichurin, D. Viehland and G. Srinivasan, J. Elec. Ceramics \textbf{19}, 243 (2007). [Preview Abstract] |
Thursday, March 19, 2009 11:51AM - 12:03PM |
W28.00002: Electric-field-induced magnetic domain wall motion in bilayer FeGa/BaTiO3 thin film structures John Cumings, T. Brintlinger, S.-H. Lim, Y. Qi, L. Salamanca-Riba, I. Takeuchi We have studied electromechanical coupling induced magnetic domain motion in unclamped FeGa/BaTiO3 thin film bilayer structures. Magnetostrictive FeGa layers were sputter-deposited on epitaxially grown BaTiO3 films on SrTiO3 substrates. Focused ion-beam milling was used to remove the substrate from underneath the BaTiO3 film, and electrodes were patterned in the metallic FeGa film to apply electric field across a patterned gap (1 micron). Lorentz microscopy was used to monitor the magnetic domains in FeGa, while electric field is applied to the piezoelectric BaTiO3. Lorentz microscopy allows direct and dynamic observation of magnetic domain motions. Reversible electric field induced magnetic domain motion was observed, and the results will be compared to micromagnetic simulations of the domain wall structure. [Preview Abstract] |
Thursday, March 19, 2009 12:03PM - 12:15PM |
W28.00003: Ferroelectric control of magnetization in BiFeO3/CoFe heterostructures. Martin Gajek, Lane Martin, John Heron, Jan Seidel, Ramamoorthy Ramesh The cross coupling between ferroic order parameters in multiferroics opens an alternative for the control of magnetism in magnetoelectric devices by purely electrical means. We first report on the exchange coupling between BiFeO3, an antiferromagnetic ferroelectric , and CoFe. We then show that the domain structure of the ferromagnet can be changed by poling the ferroelectric layer. Finally, we will discuss the implementation of our findings into possible device schemes. [Preview Abstract] |
Thursday, March 19, 2009 12:15PM - 12:27PM |
W28.00004: Induced magnetization in ferroelectric-antiperovskite heterostructure Pavel Lukashev, Renat Sabirianov We theoretically predict the linear magnetoelectric effect (ME) in ferroelectric-antiperovskite PbTiO$_{3}$/Mn$_{3}$GaN heterostructure. The effect is caused by the recently reported piezomagnetic nature of the Mn$_{3}$GaN. Elastic deformations in the Mn$_{3}$GaN are due to the surface strain and the soft mode atomic displacements from~ferroelectric to the antiperovskite (AP) phase. Both mechanisms lower the symmetry of the AP component, which results in the induced magnetization. Reversal of the polarization direction in the ferroelectric phase results in the magnetization reversal in Mn$_{3}$GaN, thus the observed effect is linear. We study few interface geometries to account for the electrostatic complementarity at the surface. Those interfaces, which are electrostatically incompatible exhibit strong tetragonal distortion of the cell. The induced magnetization depends on the termination of the components of the heterostructure, and ranges from 0.25 $\mu _{B}$ to 0.6 $\mu _{B}$ per unit cell of Mn$_{3}$GaN. All calculations were performed by projector augmented wave method. [Preview Abstract] |
Thursday, March 19, 2009 12:27PM - 12:39PM |
W28.00005: Magnetoelectric Coupling in Complex Oxide Heterostructures Jason Hoffman, Carlos Vaz, Hajo Molegraaf, Jean-Marc Triscone, Charles Ahn Current efforts to use materials with multifunctional capabilities have renewed interest in multiferroics, which display a coupling between ferroic order parameters. Engineered structures that combine dissimilar magnetic and ferroelectric systems epitaxially have been shown to exhibit enhanced magnetoelectric coupling. In this work, off-axis RF magnetron sputtering was used to deposit epitaxial ferroelectric Pb(Zr,Ti)O$_3$ (PZT) / La$_{0.8}$Sr$_{0.2}$MnO$_3$ (LSMO) heterostructures with high crystalline quality and atomically smooth surfaces. X-ray diffraction shows c-axis oriented growth of PZT, with a typical root-mean-square (RMS) surface roughness of ~5\AA. We employ magneto-optic Kerr effect (MOKE) magnetometry to study directly the local magnetic state of the LSMO as a function of the PZT polarization state. We demonstrate direct control of magnetism via applied electric fields, including on/off switching of magnetism. The coupling between magnetic and electric order parameters in ferroelectric / Sr-doped lanthanum manganite heterostructures is illustrated by hysteretic M-E (magnetization vs. electric field) loops, with a measured magnetoelectric susceptibility of $\alpha \sim 1 $Oe cm / kV$^{-1}$. [Preview Abstract] |
Thursday, March 19, 2009 12:39PM - 1:15PM |
W28.00006: GaMnAs-based hybrid multiferroic memory device Invited Speaker: A rapidly developing field of spintronics is based on the premise that substituting charge with spin as a carrier of information can lead to new devices with lower power consumption, non-volatility and high operational speed. Despite efficient magnetization detection, magnetization manipulation is primarily performed by current-generated local magnetic fields and is very inefficient. Here we report a novel non-volatile hybrid multiferroic memory cell with electrostatic control of magnetization based on strain-coupled GaMnAs ferromagnetic semiconductor and a piezoelectric material. We use the crystalline anisotropy of GaMnAs to store information in the orientation of the magnetization along one of the two easy axes, which is monitored via transverse anisotropic magnetoresistance. The magnetization orientation is switched by applying voltage to the piezoelectric material and tuning magnetic anisotropy of GaMnAs via the resulting stress field. [Preview Abstract] |
Thursday, March 19, 2009 1:15PM - 1:27PM |
W28.00007: Exchange Coupling across BiFeO$_{3}$/La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ Interface Pu Yu, M. Huijben, M.B. Holcomb, C.H. Yang, Q. He, Y. H. Chu, J. X. Zhang, L. W. Martin, R. Ramesh, Per-Anders Glans, J. H. Guo Controlling the magnetic state by using electric field is a central topic for spintronics and has piqued intense interest. The coupling of antiferromagnetic and ferroelectric order parameters of multiferroic BiFeO3 (BFO) provides a new approach to achieve this goal by using exchange coupling effect. Our previous studies have shown negative exchange bias between epitaxial ferromagnetic La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ (LSMO) and BFO heterostructures and magnetoelectric coupling at these interfaces. The coupling mechanism between these two materials is still a mystery due to the complexity of the G-type spin structure. In this work, by controlling the domain structures of BFO and studying the corresponding exchange coupling effect, the possible coupling mechanism of antiferromagnetic and ferromagnetic spin structures will be proposed. Additionally, the coupling of orbitals across the interface will also be discussed, which will give us another possible clue to understand the spin coupling mechanism, since usually orbital and spin orders are coupled together. [Preview Abstract] |
Thursday, March 19, 2009 1:27PM - 1:39PM |
W28.00008: Electric field tuning of magnetic properties in FeGa films on ferroelastic Pb(Zr,Ti)O$_{3}$ thin films probed by ferromagnetic resonance Arun Luykx, Samuel Lofland, Varatharajan Anbusathaiah, Valanoor Nagarajan, Fransiska Kartawidjaja, John Wang, Ichiro Takeuchi In order to investigate the possibility of fabricating electric field tunable thin film magnetic devices using a multiferroic transduction effect, we have patterned Fe$_{0.7}$Ga$_{0.3}$ (FeGa) films sputter-deposited on PbZr$_{0.3}$Ti$_{0.7}$O$_{3}$ (PZT(30/70))/PbZr$_{0.7}$Ti$_{0.3}$O$_{3}$ (PZT(70/30)) tetragonal/rhombohedral bilayers on Pt/Ti/SiO$_{2}$/Si wafers. Previous piezoforce microscopy studies have shown that the PZT bilayers exhibit presence of ferroelastic domains where the fraction of the local $c$/$a$ domain ratio can be tuned by an applied electric field. The FeGa top layer was patterned into 20 $\mu $m x 20 $\mu $m capacitor devices in order to apply electric field to the multilayers, and ferromagnetic resonance (FMR) measurements at 9.2 GHz were performed. Typically, a relatively sharp FMR signal observed before application of the electric field would get substantially broadened after initial application of +4 kV/cm. Angular dependent FMR indicates that magnetic anisotropy in the FeGa is indeed affected by application of electric field. [Preview Abstract] |
Thursday, March 19, 2009 1:39PM - 1:51PM |
W28.00009: Magnetoelastic/piezoelectric laminated structures for tunable remote contact-less magnetic sensing and energy harvesting Peter Finkel We report a method for tunable, contact-less, magnetic field sensing using magnetoelastic coupling properties of the magnetoelastic/piezoelectric laminated composite structure. The magnetically tunable, flexural resonant mode in the bimorph FeNi36{\%} (invar) /PVDF clamped cantilever has been investigated as a function of stress and external magnetic field using Doppler laser spectroscopy. Here we demonstrated that this bimorph structure can be used for low frequency contact-less detection of magnetic field fluctuation and magnetic field monitoring. [Preview Abstract] |
Thursday, March 19, 2009 1:51PM - 2:03PM |
W28.00010: Electrical and magnetic properties of BiFeO$_{3}$-CoFe$_{2}$O$_{4}$ nanotube composite Chandran Sudakar, Ambesh Dixit, Moodakare Bheema Sahana, Gavin Lawes, Ratna Naik, Vaman M. Naik We report the electrical and magnetic properties of BiFeO$_{3}$ and CoFe$_{2}$O$_{4}$ nanotube composite multiferroics. CoFe$_{2}$O$_{4}$ nanotubes were prepared on Pt coated Si substrates using a template assisted method, yielding nanotubes with 20-50 nm thick walls and an outer diameter of 200 to 400 nm. These nanotubes were then uniformly coated by a BiFeO$_{3}$ layer by a metal organic decomposition method to yield the composite multiferroics. We observed ferroelectric switching behavior with saturated hysteresis loops with $P_{r}$ and $E_{c}$ values of approximately 0.08 \textit{$\mu $}C/cm$^{2}$ and 15 kV/cm, respectively, for a maximum applied electric field of 50 kV/cm. For pure BiFeO$_{3}$ thin films the hysteresis curves do not show any saturating trend and the E$_{c}$ is three times smaller than that of the composite. The magnetic measurements show that the pure BiFeO$_{3}$ is non-ferrimagnetic, while the composite shows a clear hysteresis with saturation magnetization of $\sim $12 emu/cm$^{3}$. These composite BiFeO$_{3}$ -- CoFe$_{2}$O$_{4}$ structures provide an approach for studying magnetoelectric coupling at the interfaces between different ferroic materials. [Preview Abstract] |
Thursday, March 19, 2009 2:03PM - 2:15PM |
W28.00011: Multiferroic tunnel junctions: Prediction of four resistance states from first-principles J.P. Velev, C.-G. Duan, J.D. Burton, A. Smogunov, M.K. Niranjan, E. Tosatti, S.S. Jaswal, E.Y. Tsymbal Electron tunneling and ferroelectricity have had long but separate histories. In the past decade both attracted significant interest due to application in electronic devices such as magnetic tunnel junctions (tunneling) and ferroelectric capacitors (ferroelectricity) relevant to non-volatile random-access memories. Recently, driven by demonstrations of ferroelectricity in ultrathin films, it was proposed to combine these two phenomena in a multiferroic tunnel junction (MFTJ) utilizing a ferroelectric barrier between two magnetic electrodes. Due to sensitivity of the conductance to both the magnetization alignment of the electrodes (magnetoresistance) and orientation of the polarization in the ferroelectric barrier (electroresistance), this junction can serve as a four-state resistance device. Here based on first-principles calculations we demonstrate the existence of the four resistance states in SrRuO$_{3}$/BaTiO$_{3}$/SrRuO$_{3}$ MFTJs with asymmetric interfaces. We find that the resistance of such a MFTJ is significantly changed when the electric polarization of the barrier is reversed and/or when the magnetizations of the electrodes are switched from parallel to antiparallel. These results reveal exciting prospects of MFTJs for application in multifunctional electronic devices. [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