2021 Annual Report of the IUCr Commission on Magnetic Structures
Because the IUCr Congress and General Assembly (GA) in Prague were delayed by one year (2020 to 2021), the commission enjoyed a four-year term rather than the usual three-year term. At this congress, Gabriela Aurelio (Argentina), Francoise Damay (France), Dmitry Khalyavin (UK), and Noriki Terada (Japan) were elected as new voting members of the commission, while Juan Rodriquez-Carvajal (France) and Taku J Sato (Japan) stepped down from the voting membership after many years of service. This reflects a net increase of two members, which increase was proposed by the commission and approved by the GA. The voting membership of the commission now includes Gabriela Aurelio (Argentina), Maxim Avdeev (Australia), Branton J. Campbell (USA, Chair), Francoise Damay (France), M. Teresa Fernandez-Diaz (France), Ovidiu Garlea (USA), Margarida Henriques (Czech Republic), Dmitry Khalyavin (UK), J. Manuel Perez-Mato (Spain), Noriki Terada (Japan), Andrew Wills (UK), Oksana Zaharko (Switzerland).
Mois I. Aroyo (Spain), Javier Campo (Spain), Daniel B. Litvin (USA), Alexander N. Pirogov (Russia), Wieslawa Sikora (Poland) continue to serve as consultants to the commission, and are now joined by Taku J Sato (Japan) and Juan Rodriquez-Carvajal (France), who were previously voting members, as well as three new participants: Sudhindra Rayaprol (India), Oscar Fabelo (France), Bob Von Dreele (USA).
This diverse team of members and consultants provide international scientific leadership by (1) developing and maintaining standards, software, and other infrastructure for magnetic crystallography, (2) fostering magnetic-structure research communities in every part of the world, and (3) supporting the editorial and publication efforts of IUCr Journals, (4) encouraging high-quality magnetic-structure content at research meetings around the world, and by (5) organizing workshops and schools for training the next generation of early-career scientists. We note that the consultants to the commission greatly enhance its geographic reach, core expertise, coherent infrastructure development, and training capacity.
IUCr Congress Program in Prague
Despite the obstacles presented by the SARS-CoV-2 pandemic, the IUCr Congress and General Assembly in Prague were held successfully in a hybrid format in August 2021. We express gratitude to the congress for persevering and overcoming these challenges. When the congress was delayed from August 2020 to August 2021, most microsymposia and keynote-speaker sessions went forward as originally planned, though there were a few minor changes in the session descriptions and co-chairs. We note that in addition to the commissions’ seven formally sponsored microsymposia and one sponsored keynote address, four other sessions had strong magnetic-crystallography themes. Participation was generally high in each of these sessions. We thank the co-chairs of each session for attracting and selecting excellent speakers. Commission-nominated keynote speaker, Harold T. Stokes (USA), gave a highly engaging address entitled “The Science of Symmetry Breaking: A Personal Journey”. We thank Oksana Zaharko, our representative to the congress’s International Planning Committee, for her outstanding efforts to organize such a successful scientific program.
Standard and data development
The anticipated article on the development of magnetic Hall symbols appeared in print in early 2021: “Extension of Hall symbols of crystallographic space groups to magnetic space groups”, J. González-Platas, N.A. Katcho and J. Rodríguez-Carvajal, J. Appl. Cryst. 54, 338-342 (2021). This effort was spearheaded by commission member, Juan Rodriguez-Carvajal.
During the summer, the commission renewed the multi-year discussion of a new system of symbols for the 1651 three-dimensional magnetic space groups (MSGs). Based on the largely positive commission feedback received on recent adjustments to the earlier 2018 proposal, B.J. Campbell, H.T. Stokes, J.M. Perez-Mato and J. Rodriguez-Carvajal finalized the details and prepared an article for publication: “Introducing a unified magnetic space-group symbol”. The new unified (UNI) MSG symbol, which combines a modified Belov-Neronova-Smirnova (BNS) symbol with essential information from the Oppechowski-Guccione (OG) symbol, is intended to (1) follow the Hermann-Mauguin conventions used in the International Tables for Crystallography, (2) clearly convey the magnetic point group (MPG) of the MSG, (3) communicate the translational part of the time-reversal generator of each type-4 MSG, (4) separate the time-reversal from other generators for clarity, (5) distinguish each type-1 MSG from the corresponding non-magnetic space group, (6) and reveal the conventional lattice centering of both the MSG itself and the underlying non-magnetic space group. The paper appeared in print in January 2022 (Acta Cryst. A78, 99-106).
After three years of public beta testing within the ISOTROPY Software Suite, during which several problems were detected and resolved, Campbell and Stokes prepared a manuscript describing the exhaustive enumeration and tabulation of three-dimensional magnetic superspace groups with up to three independent modulations (over 325,000 groups). The MSSG symbols presented in this work are based on and compatible with the new UNI MSG symbols. This work is also expected to appear in print in 2022.
The Bilbao Crystallographic Server’s MAGNDATA collection of magnetic structures has now expanded to include over 1700 magnetic structures, including 140 incommensurate magnetic structures. The commission discussed possible approaches to turning this database into an exhaustive collection of magnetic structures. A recent feature was added to the MAGNDATA site, which allows users to submit magnetic structures themselves. It is hoped that this feature will help to distribute the workload of curating the required information.
A combination of scientific meetings, schools, and workshops supported by the commission include the following:
- American Crystallographic Association (virtual sessions on “Quantum materials” and “Magnetic Structure Determination”), 31 Jul – 05 Aug, (lecturer: Branton Campbell).
- Undergraduate Summer School on Magnetism and Magnetic Materials (virtual format), 8‐15 Aug 2021, Florida State University, Tallahassee, Florida, USA (lecturer: Ovidiu Garlea).
- IUCr Satellite Workshop on “Aperiodic and Magnetic structures for beginners” (hybrid format), 12-13 Aug 2021, Institute of Physics, Praha, Czech Republic (co-organizers and lecturers: Margarida Henriques, Vaclav Petricek, Juan Rodriguez-Carvajal, Manuel Perez-Mato, Bob Von Dreele, Branton Campbell, Harold Stokes).
- 25th IUCr Congress (hybrid format), 14-22 Aug 2021, Prague, Czech Republic, (program developed and supported by the entire commission).
- School on “Representational Analysis of Magnetic Structures” (RAMS 2021, hybrid format), 8-12 Nov 2021, University of Maryland, USA (lecturers: Margarida Henriques, Vaclav Petricek, Manuel Perez-Mato, Ovidiu Garlea, Andrew Wills, Bob Von Dreele, Branton Campbell).
Branton J. Campbell (Commission Chair)
J. Manuel Perez-Mato (Commission Secretary)