Magnetoelectric Interfaces and Spin Transport


One of the grand challenges in Condensed Matter and Materials Physics (CMMP) research for the next decade, as identified by the National Research Council of the National Academies, is answering the question “How will the information technology revolution be extended?” Further gains in data storage capacity and processing efficiency will likely involve approaches other than scaling, and new physical concepts will play a critical role. To address this goal, IRG2 is employing the electron spin in a synergistic combination with novel nanoscale magnetic, magnetoelectric, ferroelectric, and piezoelectric structures to yield new spin-dependent properties and unique functionalities. Novel heterostructures are studied to explore the interplay between electric polarization, elasticity, and magnetism across interfaces to uncover interesting new phenomena, such as electrically-controlled exchange bias and magnetocrystalline anisotropy. Conceptually new kinds of tunnel junctions and magnetic nanocontacts are investigated where a ferroelectric material is used as a barrier layer or as an electric gate material so that electron and spin transport may be manipulated both by electric and magnetic polarizations.


IRG 2 Research Areas:



A. Magnetoelectric and Multiferroic Nanostructures

This research theme focuses on the exploring of novel phenomena in multiferroic nanostructures. They are targeted to new interface effects which are studied in well-defined ferromagnetic/ferroelectric (FM/FE) heterostructures. The latter represent the generic basic building block for various novel device concepts where static and dynamic control of ferroic order parameters and their interplay with magnetocrystalline anisotropy determine novel functionalities. We are using complementary approaches to investigate the impact of the FE polarization and piezoelectricity on the FM state in static and dynamic regimes. The electrically controlled exchange bias is investigated using ME antiferromagnets as a pinning layer. Antiperovskite compounds and interfaces are studied, promising new magnetocrystalline anisotropy and piezomagnetic phenomena.

Topics:

  • Ferromagnet/Ferroelectric Heterostructures
  • Electrically-Controlled Exchange Bias
  • Novel Piezomagnetic Materials and Phenomena
  • Electrically Controllable Boundary Magnetization

B. Magnetoelectric Effects for Spin Transport

This research theme focuses on the exploring of new concepts of spintronics, which involves the manipulation of spin currents through magnetoelectric effects. A FE polarization is employed as a variable to affect the electron and spin transport in novel nanomagnetic structures involving FM/FE interfaces and ferroelectric barriers. Magnetoelectric oxides, resistive switching devices, and magnetic nanojunctions are investigated to uncover new physical phenomena controlling their magnetoresistive and electroresistive properties beneficial for advanced information technologies.

Topics:

  • Ferroelectric and Multiferroic Tunnel Junctions
  • Electron and Spin Transport in Magnetic Nanojunctions
  • Magnetoresistance Switching Phenomena
  • Ferroelectric-Enhanced Organic Electronics


IRG 2 Highlights:


» Nature Communications 2014
T. H. Vo, M. Shekhirev, D. A. Kunkel, M. D. Morton, E. Berglund, L. Kong, P. M. Wilson, P. A. DowbenA. Enders, and A. Sinitskii, “Large-Scale solution synthesis of narrow graphene nanoribbons,” Nature Communications 5, 3189 (2014).

» Nature Materials 2013
An international team of scientists, including Nebraska MRSEC physicists Evgeny Tsymbal, Alexei Gruverman and J. D. Burton, has discovered a new approach to realize giant resistive switching, as reported in Nature Materials and featured in the UNL press release (Febr. 2013). 

» APS Physics Viewpoint 2013
Christian Binek "Controlling Magnetism with a Flip of a Switch," Physics 6, 13 (2013).

» Science 2012
H. Lu, C.-W. Bark, D. Esque de los Ojos, J. Alcala, C. B. Eom, G. Catalan, and A. Gruverman, "Mechanical Writing of Ferroelectric Polarization," Science 6, 59-64 (2012). Featured on NSF Discoveries web page.
Listen to Alexei Gruverman's interview on the April 6th Science podcast.

» Nature Materials 2012
Evgeny TsymbalSpintronics: Electric Toggling of Magnets”, Nature Materials 11, 12-13 (2012) .

» Nature Materials 2011
Y. Yuan, T. J. Reece, P. Sharma, S. Poddar, S. Ducharme, A. Gruverman, Y. Yang, and J. Huang, “Efficiency enhancement in organic solar cells with ferroelectric polymers,” Nature Materials 10, 296-302 (2011).

» Nano Letters 2011
A. Mardana, S. Ducharme, and S. Adenwalla, “Ferroelectric Control of Magnetic Anisotropy,” Nano Letters 11 (9), 3862-3867 (2011).

» Invited MRS Review 2011
E. Y. Tsymbal, A. Gruverman, V. Garcia, M. Bibes, and A. Barthélémy, : “Ferroelectric and Multiferroic Tunnel Junctions,” MRS Bulletin 37, 138-43 (2012).

» Physical Review Letters 2011
N. Wu, X. He, A. L. Wysocki, U. Lanke, T. Komesu, K. D. Belashchenko, C. Binek, and P. A. Dowben, “Imaging and control of surface magnetization domains in a magnetoelectric antiferromagnet,” Phys. Rev. Lett. 106, 087202 (2010).

» Nature Materials 2010
Xi He, Yi Wang, Ning Wu, Anthony N. Caruso, Elio Vescovo, Kirill Belashchenko, Peter Dowben, and Christian Binek, "Robust isothermal electric control of exchange bias at room temperature"
Nature Materials 9, 579-585 (2010). Featured on NSF Discoveries web page.

» Physical Review Letters 2010
K. D. Belashchenko
, "Equilibrium Magnetization at the Boundary of a Magnetoelectric Antiferromagnet" Phys. Rev. Lett. 105, 147204 (2010).

» Nature Materials 2009
Stephen Ducharme and Alexei GruvermanFerroelectrics: Start the presses” Nature Materials 8, 9-10 (2009).

» Journal of Physics: Condensed Matter - Top 20 special issues (20th anniversary JPCM) (Nov. 2009)
Half-Metallic Ferromagnets” edited by Peter Dowben

» Nano Letters 2009
A. Gruverman, D. Wu, H. Lu, Y. Wang, H. W. Jang, C. M. Folkman, M. Ye. Zhuravlev, D. Felker, M. Rzchowski, C.-B. Eom and E. Y. Tsymbal,"Tunneling Electroresistance Effect in Ferroelectric Tunnel Junctions at the Nanoscale," Nano Lett. 9 (10), 3539–3543 (2009). (Nanowerk News)

IRG2

 

 


IRG 2 Researchers

Christian Binek (coordinator) - Molecular Beam Epitaxy (MBE), magnetic heterostructures, spintronics

Shireen Adenwalla - Nanofabrication, multilayers and e-beam (Neutron Scattering)

Kirill Belashchenko - Electronic structure theory

Peter Dowben - Spectroscopy and surface characterization

Stephen Ducharme - Structural and electrical characterization, Langmuir-Blodgett

Alexei Gruverman - Scanning Probe Microscopy

Jody Redepenning - Chemistry, cluster

Mathias Schubert - Pulsed laser deposition (PLD)

Andrei Sokolov - Nanofabrication, electrical and magnetic characterization

Evgeny Tsymbal - Theory of spin transport and magnetoelectric phenomena