Ultrafast all-optical manipulation of a multiferroic state

    Prof. Dr. Manfred Fiebig
ETH Zurich
Department of Materials
HCI E488.1
Vladimir-Prelog-Weg 4
8093 Zurich
Laboratory for Multifunctional Ferroic Materials
Tel. +41 44 633 2690 
Project starts   1.2.2016
Project ends    30.6.2018
Goals   Analysis of the time-dependent magnetoelectric transition into, out of, and in between multiferroic phases using reversible switching with photomagnetic pulses.
Christian Tzschaschel

Prof. Takuya Satoh
Department of Physics
Kyushu University
Fukuoka 812-8581
Abstract    After initial efforts focused on exploring and understanding the demagnetization dynamics of ferromagnets, recent trends are pointing towards new systems and objectives. Instead of restricting ourselves to the dynamics of ferromagnets we now discuss the dynamics of systems with strong electronic correlations in general. Examples are the ultrafast response of antiferromagnets, Mott insulators, or superconductors that are now explored. As another trend, consideration of energy deposition and transfer stimulated by the optical excitation is now complemented by investigation of processes in which the light field manipulates the properties of a system in a predominantly non-thermal way. An example is the manipulation of magnetization via the magnetic field generated by the transmitted light wave via magneto-optical rectification. Our project builds on these emerging trends.

We propose to explore the dynamical response of multiferroics, i.e., of materials uniting magnetic and ferroelectric order in the same phase. Multiferroics can display exceptionally strong cross-coupling effects between the magnetic and electric properties. A major goal is magnetization control employing electric fields instead of current-driven magnetic fields, which avoids the notorious problem of waste-heat production. One would assume that with voltage-driven magnetization reversal as main target of multiferroics research, the temporal evolution of such "magnetoelectric writing" is well explored. Most surprisingly, this is not the case: There are barely a handful of disjointed reports on this issue. With our project we will explore the ultrafast magnetoelectric dynamics of MnWO4 as a representative of the class of multiferroics exhibiting the strongest magnetoelectric coupling. We will excite the samples by a magnetic field pulse generated optically and study the ensuing dynamics in the magnetic and electric subsystem via nonlinear optics and Brillouin light scattering. We will thus gain fundamental insight into the magnetoelectric correlation dynamics and their intrinsic timescales in this important class of materials and point out routes towards their implementation in devices. 
Publications   Tzschaschel, C., K. Otani, R. Iida, T. Shimura, H. Ueda, S. Günther, M. Fiebig and T. Satoh (2017). Ultrafast optical excitation of coherent magnons in antiferromagnetic NiO. Physical Review B 95: 174407 (10.1103/PhysRevB.95.174407) Tzschaschel-2017 (792 KB) Editors' Suggestion.
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