ELFT HÍRADÓ

[bordacs.sandor AT wigner.bme.hu]

Kedves Kollégák!

Szeretném figyelmükbe ajánlani a BME Fizika Tanszékének szemináriumát.

Előadó: Jonathan White – Laboratory for Neutron Scattering and Imaging, 
Paul Scherrer Institut (PSI), Switzerland

Cím: Neutron scattering explorations of new magnetoelectric coupling 
effects at PSI:
ferromagnetic ferroelectrics and skyrmion lattices

Időpont: 2015. március 30. (hétfő) 10 óra
Helyszín: BME F. épület I. lh. 1. em. Schay terem

Asztrakt: Over the last decade or so, neutron scattering has played a 
pivotal role in the study of the remarkable magnetoelectric coupling 
properties driven by symmetry-breaking magnetic order. Here we present 
two recent neutron scattering studies done at PSI that continue this 
theme.

Firstly, we will introduce our study of the magnetically-driven 
multiferroic Mn2GeO4. This material was shown by us recently to display 
a rare multiferroic phase for a bulk material, being simultaneously 
ferromagnetic and ferroelectric, with both orders spontaneous and 
pointing along the c-axis [1]. Bulk measurement techniques appear to 
show a coupling between the ferromagnetism and ferroelectricity, and we 
have undertaken neutron scattering studies with samples under applied 
magnetic and electric fields in order to clarify the new microscopic 
principles that govern such a coupling.

Secondly, we have used small-angle neutron scattering (SANS) to study 
the topologically protected magnetic spin vortices, or Skyrmions, in the 
chiral-lattice magnetoelectric insulator Cu2OSeO3. Until 2012, Skyrmions 
had been observed only in (semi)conducting B20 compounds where it is 
known that they can be manipulated by conduction electrons. From our 
SANS experiments on Cu2OSeO3 [2], we show that applied electric fields 
can control the skyrmion lattice orientation in insulators, and in an 
essentially lossless manner that is dependent on both the size and sign 
of the electric field. These results provide the first evidence for the 
electric field control of topological magnetism in magnetoelectric 
materials.

[1] J.S. White et al., Phys. Rev. Lett. 108, 077204 (2012)
[2] J.S. White et al., J. Phys.: Condens. Matter 24, 432201 (2012), 
Phys. Rev. Lett.  113, 107203 (2014)

Minden érdeklődőt szívesen látunk!

--
Dr. Sandor Bordacs
assistant prof.
MTA-BME Lendulet Magneto-optical Spectroscopy Research Group
Department of Physics, Budapest University of Technology and Economics
http://magnetooptics.phy.bme.hu
Tel: 36-1-4633056
Fax: 36-1-4634180