The former Functional Materials Group at the National Physical Laboratory and the UK-CRG XMaS beamline, based at the European Synchrotron Radiation Facility in Grenoble, France, co-hosted the first UK workshop on X-rays and neutrons in multiferroic research on 17 June 2009.
(All downloads are PDF files, unless otherwise stated, where Permission to Publish has been granted)
Event flyer (1.47 MB)
- Multiferroics & magnetoelectrics (1.48 MB)
Neil Mathur, Cambridge
- Electric field control of magnetic order in multiferroic TbMnO3 imaged with circularly polarised X-rays (2.38 MB)
Des McMorrow, UCL
- X-ray scattering techniques to explore in-situ properties of multiferroic materials (2.39 MB)
Peter Hatton, Durham
- Structure and Phase Transitions in Multiferroics: The Case of BiFeO3 (4.54 MB)
Phil Lightfoot, University of St Andrews
- Dependence of internal stress and hydrostatic pressure on the magnetic ordering in the multiferroic BiFeO3 - PbTiO3
Tim Comyn, Leeds
- Induced multiferroic behaviour in single crystals of RMnO3 Manganites (2.96 MB)
Geetha Balakrishnan, Warwick
- Stress, E field and B field in-situ measurements (2.1 MB)
Mark Stewart, NPL
- Stress, E field and B field in-situ measurements (3.63 MB)
Paul Thompson, XMaS CRG
A series of talks showing recent progress in this field was kicked off by Neil Mathur (University of Cambridge) who gave an introduction to multiferroic, magnetoelectric and ferroelectric phenomena, detailing examples of materials properties such as bismuth ferrite, which is a good room temperature FE. Crystallography studies of this material were presented by Phil Lightfoot (University of St Andrews) and Tim Comyn (University of Leeds), the former using neutron diffraction measurements to determine the atomic structure of the high temperature phases, and the latter investigating the effect of different sample processing techniques on the crystal symmetry. Doping bismuth ferrite with lead titanate results in a mixed phase compound that his strongly ferroelectric and piezoelectric - it is also possible to 'switch on' the magnetic ordering by means of an in-situ hydrostatic pressure.
The use of magnetism to control the polarisation was discussed by Des McMorrow (UCL) who used non-resonant x-ray scattering and x-ray polarimetry to deduce the magnetic structure and domain population of the multiferroic TbMnO3. Resonant x-ray scattering techniques were employed by Peter Hatton (Durham University) to look at the magnetism of a different terbium manganese oxide, TbMn2O5. The magnetic structure refinements using these techniques however, often rely on complementary neutron studies, and some examples of these in the wider class of manganese oxide materials RMn2O5 were presented by Carlo Vecchini (ISIS).
Geetha Balakrishnan (University of Warwick) discussed how the non-ferroic SmMnO3 compound could be 'tuned' into multiferroicity by doping with yttrium to force the crystallographic structure into the part of the RMnO3 phase diagram occupied by TbMnO3 and DyMnO3 - well known multiferroic compounds. She concluded by presenting neutron scattering data on the frustrated Kagome staircase compounds nickel vanadate and cobalt vanadate - previously studied for their interesting magnetic order, and only recently discovered to be ferroelectric. Since ferroelectricity is known to occur when magnetic ordering breaks inversion symmetry, magnetic insulators with modulated magnetic structures, as found in the vanadates, are ideal candidates for new multiferroic materials.
The workshop concluded with presentations by Mark Stewart (NPL) on the experimental procedures required to characterise ferroelectric materials and how these should be employed in a neutron or x-ray experiment, and Paul Thompson (XMaS/ESRF) who gave an overview of the measurement capabilities at the XMaS beamline, which is ideally suited to the study of multiferroics.
Finally, the afternoon session finished with an open discussion chaired by Bob Cernik (The University of Manchester). The group ascertained that the main experimental interests in this field focus on the ability to perform in-situ magnetoelectric and piezoelectric measurements. This workshop was a first milestone for the development of fundamental research in the field of multiferroics and x-ray/neutron scattering.