2017 Triennial Report of the IUCr Commission on Magnetic Structures
Following the Montreal Congress in August 2014, the voting members of the commission include Branton Campbell (Chair, USA), Andrea Cornea (Italy), Daniel Litvin (USA), J. Manuel Perez-Mato (Spain), Vaclav Petricek (Czech Republic), Alexander Pirogov (Russia), Vladimir Pomjakushin (Switzerland), Juan Rodriguez-Carvajal (France), Taku Sato (Japan) and Wieslawa Sikora (Poland). The commission’s consultants include: Mois Aroyo (Spain), Maria Teresa Fernandez-Diaz (Institut Laue Langevin, France), Harold Stokes (USA), and Andrew Wills (UK). At the commission meeting in Montreal, it was decided that in the coming term, Wieslawa Sikora would serve as Secretary of the commission, Danny Litvin would serve as liaison to the Commission for Nomenclature, Maria-Teresa Fernandez-Diaz would continue to serve as liaison to the Commission on Neutron Scattering, Taku Sato would manage the commission web resources, and Alexander Pirogov would lead the effort to contribute entries relevant to magnetic structure to the IUCr’s Online Dictionary of Crystallography. We congratulate Wieslawa Sikora for her recent retirement and Vaclav Petricek for receiving the European Crystallographic Association’s Perutz prize in 2016.
In addition to the in-person commission meeting in Montreal Canada on 09 Aug 2014 , annual or biannual meetings of the commission spanning 16 time zones have been conducted once or twice each year via internet-video: 11 February 2014, 24 November 2015, 08 Feb 2016, 13 Oct 2016.
The extensive efforts of commission members and consultants to plan, organize, advertise, attend, and present at the 2014 IUCr Congress in Montreal made it a hugely-successful venue for magnetic-structure community. Wieslawa Sikora (AGH University of Science and Technology, Poland), the commissions representative to the Congress IPC helped to secure a scientific program that included 14 directly-relevant keynote addresses and microsymposia, 8 of which were co-sponsored by the commission, and nearly all of which were supported in some way (e.g. organizer, chair, presenter, etc.) by commission members. These sessions were well attended (completely full in some cases), and the presentation quality was generally very high.
- Multiferroics, keynote lecture by Tsuyoshi Kimura
- Small angle scattering for magnetism and magnetic structures, chaired by Joachim Kohlbrecher and Andreas Michels
- Magneto-structural relationships in molecular compounds, chaired by Andrea Cornea and Barbara Sieklucka.
- Commensurate & incommensurate multiferroics and magnetoelectrics: structure and properties*,
chaired by Radoslaw Przenioslo and Hiroyuki Kimura
- Commensurate and Incommensurate Multiferroics: Structure and Properties, keynote by Laurent Chapon
- Symmetry constraints in magnetic structure determination: experiment and theory, chaired by Branton Campbell, Mois Aroyo
- Electronic and magnetic phenomena at extreme conditions, chaired by Karen Friese, Karel Prokes
- The expanding scope of crystallographic representation analysis, keynote lecture by Branton Campbell
- Sixty Five Years of Magnetic Structures: Present and Future of Magnetic Crystallography, keynote lecture by Juan Rodriguez-Carvajal
- Cross-disciplinary Investigations of Structural and Magnetic Properties of Materials by Solid-State NMR and Diffraction Techniques, chaired by J. M. Gillet and Francis Taulelle
- Pushing the Boundaries of Aperiodic Magnetic & Crystal Structure Solution, chaired by Vaclav Petricek and Walter Steurer
- Structural, Electronic and Magnetic Ordering: From Fundamental Physics to Functionality, chaired by Yuichi Shimakawa and Paul Attfield
- X-ray, muon and neutron studies of magnetic structure in materials, chaired by Youchi Murakami and Oksana Zaharko
- Frustration, topology and chirality in metals and complex oxides, chaired by Taku Sato and Laurent Chapon
Taku Sato (Tohoku University, Japan), the commission representative to the 2017 Congress IPC, travelled to Hyderabad India in March 2016 to negotiate the program for the upcoming congress, and was similarly successful. We anticipate 13 sessions at the Hyderabad congress with strong magnetic-structure themes, 9 of which were either sponsored or co-sponsored by the commission.
The commission continues to actively discuss three common methods of describing a magnetic structure: the commensurate-supercell description, the incommensurate-wave description (a.k.a. propagation-vector description), and the representational (group-theoretical) description. Each description type has a distinct parameter set, which if treated in a fully general way, can be converted into any of the other descriptions. And each description can be executed with or without taking magnetic symmetry into account. The new magCIF dictionary developed primarily by commission members has been the principle arena for forging consensus on magnetic-structure descriptions since the commission was formed in 2011.
During the past three years, commission members in the magCIF working group (Branton, Manu, Vaclav, Juan, Wieslawa) generated numerous revisions to the prototype dictionary, including (1) the addition of support for incommensurate structures, which had been negotiated during the previous year, (2) improvements to entries involving Opechowski-Guccione (OG) and Belov-Neronova-Smirnova (BNS) settings of commensurate magnetic space groups, (3) changes to entries that describe commensurate and incommensurate setting transformations, (4) the use of magnetic propagation vectors within descriptions that employ OG-settings, (5) entries supporting the definition of a parent-structure, (6) symmetry constraints on structural parameters, and (7) many more minor changes. Some of these issues involved lengthy debates and discussions. The collaboration with COMCIFS chair, James Hester, to convert our custom-markup version of magCIF into a proper DDLm dictionary began in earnest in March 2016. This process required some significant and even painful changes to the planned tag structures in the dictionary, as a prototype tag set was already in use by several widely-used software packages. The new dictionary was submitted to COMCIFS for review in September, and was approved on 31 October 2016. Preparations to take the dictionary online require some infrastructure development, but will hopefully be complete before the upcoming Congress in Hyderabad. The magCIF format is already employed by a number of software packages and tools, including FullProf, JANA, the Bilbao Crystallographic Server, the ISOTROPY suite, Vesta, JMol, and others. Ideally, all magnetism-capable structural-analysis packages should be able to exchange final-version magCIF files. Assignments to coordinate with a variety of software developers were delegated to working-group members.
The MAGNDATA database of magnetic structures hosted by the Bilbao Crystallographic Server team now contains over 400 published commensurate and incommensurate structures, each of which is unambiguously presented with magnetic space-group or superspace-group symmetry in the magCIF format, and ready to be immediately visualized and or exported to a variety of other software packages. This effort builds upon the well-known work of Sikora and Oles. See S.V. Gallego et al., J. Appl. Cryst. (2016), 49, 1750-1776 and 1941-1956 for recent articles on the progress of the MAGNDATA project.
To celebrate the International Year of Crystallography, the commission conducted a three-day workshop on “The Role of Magnetic Symmetry in the Description & Determination of Magnetic Structures” (https://magcryst.org/meetings/cmsworkshop2014) on 14-16 August 2014 at the Brockhouse Institute for Materials Research at McMaster University in Hamilton, Canada. This satellite meeting of the 2014 IUCr Congress had 46 participants (including 8 presenters) from 29 institutions from 15 countries and 6 continents (Argentina, Australia, Belgium, Canada, Czech Republic, France, Germany, India, Norway, South Korea, Spain, Sweden, Switzerland, UK, USA). The workshop combined the practical aspects of magnetic structural analysis (e.g. analytical software tools and neutron scattering instruments) with the theoretical foundations of magnetic crystallography (e.g. magnetic symmetry groups, tensor properties, and matrix representations). Hands-on tutorials emphasized new magnetic-structure capabilities of the JANA, FullProf, TOPAS, Bilbao Crystallographic Server, and ISOTROPY Suite tools and resources. Lectures demonstrated the application of these novel capabilities to a variety of interesting structures.
A one-week workshop on New Trends in Magnetic Structure Determination (12-16 Dec 2016, Institute Laue Langevin, Grenoble France, https://indico.ill.fr/indico/event/53/overview) was sponsored by the commission, which highlighted the magCIF format and other new infrastructure for magnetic-structure descriptions developed by the commission during the past five years. The meeting was organized by Juan Rodriguez Carvajal and Oscar Fabelo, and generously supported by the ILL. Lectures and tutorials were given by Laurent Chapon and Juan Rodriguez-Carvajal (FullProf), Vaclav Petricek (JANA), J. Manuel Perez Mato (Bilbao Crystallographic Server), and Harold Stokes and Branton Campbell (ISOTROPY Suite). Of the 60 applicants, 40 were selected to attend. Most participants were accomplished magnetic neutron scatterers aiming to stay abreast of recent developments. The focus of the meeting was on new software capabilities for treating magnetic space-group and superspace-group symmetry, magnetic representation analysis, fully-general magnetic structures, incommensurate magnetic modulations. An underlying theme throughout the workshop was the use of the new magCIF format for communicating magnetic-structure information between a variety of structure-analysis programs, visualization packages, and data resources.
During the years 2014-2016, the commission has encouraged high-quality magnetic-structure research through the support of over 30 national and international conferences, schools, and workshops. This support by the commission and its individual members and consultants has included sponsorship, direct meeting organization, grant writing, organization and/or chairing of conference sessions, workshop presentations, and both invited and contributed lectures.
Tentative future plans and interests of the commission include the following:
(1) Expand efforts to educate the crystallographic and broader structural-science communities in the art of unambiguously and concisely describing a magnetic structure.
(2) Promote the wide-spread adoption of the magCIF standard amongst crystallographic software developers.
(3) Extend magCIF to support magnetic structure factors, magnetic reflection conditions, low-dimensional magnetic order, short-range magnetic order, etc. Possibly support rotational moments in parallel with magnetic moments, both of which are axial vectors.
(4) Support the development of tools that convert between OG and BNS presentations of a commensurate magnetic-structure (in magCIF format), and between commensurate-supercell and incommensurate-wave descriptions of a commensurate magnetic structure.
(5) Explore the possibility of a new standard for magnetic-space-group symbols.
(6) Develop a representation-analysis CIF dictionary that provides for the complete description of a magnetic or non-magnetic structure in terms of basis functions of irreducible representations of a relevant higher-symmetry parent structure.
(7) Debate long-term strategies for supporting and preserving computational tools and data resources relevant to the determination and communication of magnetic structures.
(8) Prepare a new volume of the International Tables of Crystallography that focuses on magnetic symmetry, magnetic diffraction, and magnetic structures.
Branton J. Campbell