Magnetoelectric (ME) materials are at the frontier of materials research due to a variety of non-trivial coupling mechanisms interweaving electric and magnetic degrees of freedom. Their properties are in many aspects superior over today’s spintronic materials where the emphasis is on creating and manipulating spin-polarized (but nevertheless dissipating) electric currents. Controlling ME coupling on the nanoscale enables unprecedented possibilities to tailor functional materials and complex nanostructures, thus opening unique perspectives for novel technologies where electrically controlled magnetism offers innovative approaches for device operation.
The primary objective of this IRG is to understand magnetoelectricity in complex functional heterostructures and enable its unconventional use beyond the realm of static equilibrium and linear response. This objective will be achieved through interdisciplinary investigations of ME antiferromagnets, complex oxide thin films, ME multiferroics, and molecular-level magnetoelectrics. They will be implemented in new functional heterostructures and subject to external stimuli giving rise to responses in a hitherto unexplored parameter space. The expected research outcomes are new insights in the ME coupling and spin dynamics of magnetoelectrics, development of novel voltage-controlled ultra-low power spintronic devices, and harnessing voltage-controlled entropy changes in conceptually new materials design.
IRG 1 Researchers
Christian Binek (coordinator) - MBE, PLD, Magnetometry
Shireen Adenwalla - Sputtering, XMCD, Kerr
Kirill Belashchenko - Theory transport, magnetoelectricity
Peter Dowben - Photoemission, XMCD
Axel Enders - STM, XMCD
Tino Hofmann- THz Ellipsometry
Xia Hong - Sputtering, TransportDhananjay Kumar - Magnetometry
Jeffrey Shield - HRTEM
Xiaoshan Xu - PLD, n0-scattering
Jian Zhang - Chemical synthesis
Research Thrust 1:
Dynamic Straindriven Phase Transitions
Thrust 1 explores dynamic strain-driven phase transitions and entropy changes in ME bulk materials and thin films. Here the full potential of ME coupling beyond the linear static regime is exploited.
- ME boundary magnetization and antiferromagnetic order
- Oxides with strain sensitive metal-insulator transition
- Electromagnon dispersion
- Magnetocaloric effect
Research Thrust 2:
Functional Magnetoelectric Materials and Interfaces
Thrust 2 utilizes ME heterostructures and materials for fundamental investigations of voltage-controlled interface and bulk magnetic states and paves the way for the development of ultra-low power non-volatile memory applications, where switching of magnetic state variables by electrically driven non-linear processes is a key phenomenon.
- Detecting ME boundary magnetization
- Hexagonal ferrite films as ME active materials
- Electric field control of interface magnetic anisotropy and exchange bias
Research Thrust 3:
Thrust 3 explores novel molecular-level magnetoelectrics where local and external electric fields are used to switch organic spin crossover molecules and to control and characterize the magnetism of nanoclusters and thin films. Here the basic concepts of Thrusts 1 and 2 are extrapolated down to the scale of individual molecules.
- Spin-crossover molecular overlayers
- Tailoring magnetism of metal nanoclusters by single dipolar molecule ligands
IRG 1 Highlights:
» Nature Communications 2014
T. H. Vo, M. Shekhirev, D. A. Kunkel, M. D. Morton, E. Berglund, L. Kong, P. M. Wilson, P. A. Dowben, A. 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).
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 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).
» 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.