X-ray & Neutron Scattering in Multiferroics Research

These yearly, one day meetings are designed bring together experts from the multiferroics, magnetoelectrics and ferroelectrics communities with neutron and synchrotron facility users to present the latest developments in this field. The meetings are held at NPL.

First meeting held at NPL on 17th June 2009

The Functional Materials Group at the National Physical Laboratory[1], and the UK-CRG XMaS beamline* based at the European Synchrotron Radiation Facility in Grenoble, France[2] co-hosted the first UK workshop on x-rays and neutrons in multiferroic research on 17th June 2009. A series of talks showing recent progress in this field was kicked off by Neil Mathur (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 (St. Andrews) and Tim Comyn (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) to look at the magnetism of a different terbium manganese oxide, TbMn2O5. The magnetic structure refinements using these techniques however, often rely on complimentary neutron studies, and some examples of these in the wider class of magnese oxide materials RMn2O5 were presented by Carlo Vecchini (ISIS). Geetha Balakrishnan (Warwick) discussed how the non-ferroic SmMnO3 compound could be “tuned” into multferroicity 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 such 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 (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 (Manchester). The group ascertained the main experimental interests in this field focus on the ability to perform in-situ magnetoelectric and piezoelectric measurements. NPL have created this website with the aim of centralising all the information required to perform a multiferroic neutron/x-ray experiment – from best practice guides on sample preparation and electrode deposition techniques, to experimental beamline descriptions designed to help the user choose the right measurement technique for the right experiment. Additionally, users are encouraged to contribute information on their experimental successes and failures, so that their experience will help the rest of the community avoid making costly mistakes, as beamtime at neutron and synchrotron facilities can cost upwards of €15k per day. This workshop was a first milestone for the development of fundamental research in the field of multiferroics and x-ray/neutron scattering.

The presentations from the workshop are available here

Second meeting held at NPL on 23rd September 2011

A second meeting in the X-ray & Neutron Scattering in Multiferroics Research series was held at NPL, 23rd September 2011.

The event brought together experts from the multiferroics, magnetoelectrics and ferroelectrics communities with neutron and synchrotron facility users to present the latest developments in this field. A series of presentations were given by leading researchers covering a variety of topics from fundamental physics of multiferroic switching, to X-ray experimental results and best practice. Other talks focused on the practicalities of using ferroelectrics as computer memory (RAM) and magnetic storage.

A discussion forum was held during the afternoon, to examine the experimental uncertainties concerning application in situ electric, magnetic and stress fields in x-ray and neutron experiments. Delegates also debated a wider range issues in materials processing, crystal growth and sample preparation.

The event was highly successful and brought together many leading researchers in the field for sharing of ideas and results in a pleasant, informal setting.

The following talks were presented:

• More than one twist: multiferroics and magnetoelectrics beyond the cycloidal mechanism, Paolo Radaelli (Oxford).

• In situ neutron and x-ray synchrotron studies of multiferroics, Andrew Bell (Leeds).

• Advancing the understanding of multiferroics through resonant x-ray scattering, Peter Hatton (Durham).

• In-situ studies of structure and electrical properties of BiFeO3 as a function of temperature and pressure, Bob Freer (Manchester).

• Local and average structures of new leadfree polar materials, Matthew Rosseinsky (Liverpool).

• Electric control of magnetic chirality in CuO, Andrew Boothroyd (Oxford).

• X-ray Resonant Magnetic Scattering of Strain induced Magnetoelectric EuTiO3 films., Simon Brown (ESRF).

• In situ facilities for ferroelectric and multiferroic materials at ESRF and DIAMOND., Mark Stewart (NPL).