Magnetic symmetry in the Bilbao Crystallographic Server: a computer program to provide systematic absences of magnetic neutron diffraction

2012 ◽  
Vol 45 (6) ◽  
pp. 1236-1247 ◽  
Author(s):  
Samuel V. Gallego ◽  
Emre S. Tasci ◽  
Gemma de la Flor ◽  
J. Manuel Perez-Mato ◽  
Mois I. Aroyo
Keyword(s):  
Neutron Diffraction ◽  
Computer Program ◽  
Magnetic Moments ◽  
General Information ◽  
Resolving Power ◽  
Space Groups ◽  
Magnetic Structures ◽  
Starting Point ◽  
Magnetic Symmetry ◽  
Symmetry Operations

MAGNEXTis a new computer program available from the Bilbao Crystallographic Server (http://www.cryst.ehu.es) that provides symmetry-forced systematic absences or extinction rules of magnetic nonpolarized neutron diffraction. For any chosen Shubnikov magnetic space group, the program lists all systematic absences, and it can also be used to obtain the list of the magnetic space groups compatible with a particular set of observed systematic absences. Absences corresponding to specific ordering modes can be derived by introducing effective symmetry operations associated with them. Although systematic extinctions in neutron diffraction do not possess the strong symmetry-resolving power of those in nonmagnetic crystallography, they can be important for the determination of some magnetic structures. In addition,MAGNEXTprovides the symmetry-adapted form of the magnetic structure factor for different types of diffraction vectors, which can then be used to predict additional extinctions caused by some prevailing orientation of the atomic magnetic moments. This program, together with a database containing comprehensive general information on the symmetry operations and the Wyckoff positions of the 1651 magnetic space groups, is the starting point of a new section in the Bilbao Crystallographic Server devoted to magnetic symmetry and its applications.

scholarly journals A historical introduction to the symmetries of magnetic structures. Part 1. Early quantum theory, neutron powder diffraction and the coloured space groups

2017 ◽  
Vol 32 (2) ◽  
pp. 148-155 ◽  
Author(s):  
Andrew S. Wills
Keyword(s):  
Time Reversal ◽  
Magnetic Ordering ◽  
Neutron Powder Diffraction ◽  
Quantum Mechanical ◽  
Langevin Model ◽  
Space Groups ◽  
Magnetic Structures ◽  
Black And White ◽  
Magnetic Symmetry ◽  
Looking Back

This paper introduces the historical development of the symmetries for describing magnetic structures culminating in the derivation of the black and white and coloured space groups. Beginning from the Langevin model of the Curie law, it aims to show the challenges that magnetic ordering presented and how different symmetry frameworks were developed to meet them. As well as explaining core ideas, later papers will show how the different schemes are connected. With these goals in mind, the maths related is kept to the minimum required for clarity. Those wishing to learn more details are invited to engage with the references. As well as looking back and reviewing the development of magnetic symmetry over time, particular attention is spent on explaining where the concept of time-reversal has been applied. That time-reversal has different meaning in classical and quantum mechanical situations, has created confusions which continue to propagate.

scholarly journals A collection of magnetic structures with cif-like files as a database seed

2014 ◽  
Vol 70 (a1) ◽  
pp. C1369-C1369
Author(s):  
Samuel Gallego ◽  
J. Manuel Perez-Mato ◽  
Emre Tasci ◽  
Luis Elcoro ◽  
Mois Aroyo ◽  
...  
Keyword(s):  
Magnetic Moments ◽  
Parent Phase ◽  
Point Group ◽  
Original Data ◽  
Quantitative Information ◽  
Isotropy Subgroup ◽  
Magnetic Structures ◽  
Structure Description ◽  
Magnetic Symmetry ◽  
The Cost

We report the release within the Bilbao Crystallographic server [1] of a webpage providing detailed quantitative information on a representative set of published magnetic structures. Under the name of MAGNDATA (www.cryst.ehu.es/magndata) more than 140 entries are available. Each magnetic structure has been saved making use of magnetic symmetry, i.e. Shubnikov magnetic groups for commensurate structures, and magnetic superspace groups for incommensurate ones. This ensures a unified communication method and a robust and unambiguous description of both atomic positions and magnetic moments. The origin and main crystallographic axes of the parent phase are usually kept, with the cost of often using a non-standard setting for the magnetic symmetry. The magnetic point group is also given, so that the allowed macroscopic tensor properties can be derived. The fact that magnetic structures are being described according to various methods, often with ambiguous information, has forced an elaborate interpretation and transformation of the original data. For this purpose the freely available internet tools MAXMAGN [1] and ISODISTORT [2] have been our essential tools. Most of the analyzed structures happen to possess maximal magnetic symmetries within the constraints imposed by the magnetic propagation vector, and the relevant model could be derived in a straightforward manner using MAXMAGN [1]. In a few cases a lower symmetry is realized, but then it corresponded to one isotropy subgroup of one or several irreducible representations (irreps) of the paramagnetic grey space group, and ISODISTORT [2] could be applied to model the structure. Although the structure description is done using magnetic groups, the active irrep(s) are also given in most cases. The entries of the collection can be retrieved in a cif-like format, which is supported by internet tools as STRCONVERT [1] and ISOCIF [2], the visualization program VESTA [3], and some refinement programs (JANA2006, FULLPROF). Each entry also includes Vesta files that allow the visualization of a single magnetic unit cell.

Matching selenium-atom peak positions with a different hand or origin

2002 ◽  
Vol 35 (3) ◽  
pp. 368-370 ◽  
Author(s):  
G. David Smith
Keyword(s):  
Computer Program ◽  
Iterative Procedure ◽  
Polar Axis ◽  
Polar Space ◽  
Selenium Atom ◽  
Space Group ◽  
Space Groups ◽  
Fortran 90 ◽  
Symmetry Operations

An algorithm is described for matching and correlating two or more sets of peaks or atoms. The procedure is particularly useful for matching putative selenium atoms from a selenium-atom substructure as obtained fromEmaps from two or more random-atom trials. The algorithm will work for any space group exceptP1. For non-polar space groups, the procedure is relatively straightforward. For polar space groups, the calculation is performed in projection along the polar axis in order to identify potential matching peaks, and an iterative procedure is used to eliminate incorrect peaks and to calculate the displacement along the polar axis. The algorithm has been incorporated into a computer program,NANTMRF, written in Fortran 90. Less than 0.5 s are required to match 27 peaks in space groupP21, and the output lists the correct origin, enantiomorph, symmetry operations, and provides the relative displacements between pairs of matching peaks.

scholarly journals Sixty Five Years of Magnetic Structures. Present and Future of Magnetic Crystallography

2014 ◽  
Vol 70 (a1) ◽  
pp. C24-C24
Author(s):  
Juan Rodriguez-Carvajal
Keyword(s):  
Neutron Diffraction ◽  
Magnetic Structure ◽  
Magnetic Moments ◽  
Spatial Arrangement ◽  
Physical Review ◽  
Three Dimensions ◽  
Magnetic Structures ◽  
Symmetry Properties ◽  
Special Cases

Magnetic Crystallography is a sub-field of Crystallography concerned with the description and determination of the magnetisation density in solids. A magnetic structure corresponds to a particular spatial arrangement of magnetic moments that sets up below the ordering temperature. The determination of magnetic structures is mainly done using neutron diffraction (powder and single crystals) and in special cases the use of polarized neutrons is necessary to solve ambiguities found in the interpretation of magnetic neutron diffraction data. We can consider that Magnetic Crystallography starts with the seminal paper by C.G. Shull and S. Smart on the magnetic structure of MnO published the 29 August 1949 in the Physical Review 76, 1256. The symmetry properties of periodic arrangement of atoms are well described by the 230 space group types in three dimensions, however more complex spatial arrangements of atoms may need to be described by periodicity in higher dimensions. Incommensurate, composite and quasi-crystal structures represent a relatively small part of the huge amount of materials that can be described by conventional Crystallography, however many magnetic structures are non-commensurate: the periodicity of the orientation of the magnetic moments is not commensurate with the underlying crystal structure. The symmetry properties of magnetic structures are traditionally described using two different approaches: the magnetic Shubnikov groups [1] and the group representation analysis [2-3]. In this talk we shall describe how these approaches have been established historically and the advantages of the new trend towards the use of magnetic superspace groups. A review of the most important papers and milestones in magnetic neutron scattering as well as in the symmetry concepts will be presented. The current analytical tools and methods for determining magnetic structures and their symmetry will briefly be described.

MAGNDATA: towards a database of magnetic structures. I. The commensurate case

2016 ◽  
Vol 49 (5) ◽  
pp. 1750-1776 ◽  
Author(s):  
Samuel V. Gallego ◽  
J. Manuel Perez-Mato ◽  
Luis Elcoro ◽  
Emre S. Tasci ◽  
Robert M. Hanson ◽  
...  
Keyword(s):  
Magnetic Moments ◽  
Parent Phase ◽  
Point Group ◽  
Quantitative Information ◽  
Isotropy Subgroup ◽  
Published Data ◽  
Cell Orientation ◽  
Space Group ◽  
Magnetic Structures ◽  
Magnetic Symmetry

A free web page under the name MAGNDATA, which provides detailed quantitative information on more than 400 published magnetic structures, has been developed and is available at the Bilbao Crystallographic Server (http://www.cryst.ehu.es). It includes both commensurate and incommensurate structures. This first article is devoted to explaining the information available on commensurate magnetic structures. Each magnetic structure is described using magnetic symmetry, i.e. a magnetic space group (or Shubnikov group). This ensures a robust and unambiguous description of both atomic positions and magnetic moments within a common unique formalism. A non-standard setting of the magnetic space group is often used in order to keep the origin and unit-cell orientation of the paramagnetic phase, but a description in any desired setting is possible. Domain-related equivalent structures can also be downloaded. For each structure its magnetic point group is given, and the resulting constraints on any macroscopic tensor property of interest can be consulted. Any entry can be retrieved as a magCIF file, a file format under development by the International Union of Crystallography. An online visualization tool using Jmol is available, and the latest versions of VESTA and Jmol support the magCIF format, such that these programs can be used locally for visualization and analysis of any of the entries in the collection. The fact that magnetic structures are often reported without identifying their symmetry and/or with ambiguous information has in many cases forced a reinterpretation and transformation of the published data. Most of the structures in the collection possess a maximal magnetic symmetry within the constraints imposed by the magnetic propagation vector(s). When a lower symmetry is realized, it usually corresponds to an epikernel (isotropy subgroup) of one irreducible representation of the space group of the parent phase. Various examples of the structures present in this collection are discussed.

scholarly journals Crystal and magnetic structures of R 2Ni1.78In compounds (R = Tb, Ho, Er and Tm)

2021 ◽  
Vol 77 (5) ◽  
pp. 824-832
Author(s):  
Stanisław Baran ◽  
Aleksandra Deptuch ◽  
Andreas Hoser ◽  
Bogusław Penc ◽  
Yuriy Tyvanchuk ◽  
...  
Keyword(s):  
Rare Earth ◽  
Neutron Diffraction ◽  
Magnetic Structure ◽  
Magnetic Moments ◽  
Symmetry Analysis ◽  
Crystalline Electric Field ◽  
Magnetic Structures ◽  
Antiferromagnetic Ordering ◽  
Crystal And Magnetic Structures ◽  
The Rare Earth

The crystal and magnetic structures in R 2Ni1.78In (R = Ho, Er and Tm) have been studied by neutron diffraction. The compounds crystallize in a tetragonal crystal structure of the Mo2FeB2 type (space group P4/mbm). At low temperatures, the magnetic moments, localized solely on the rare earth atoms, form antiferromagnetic structures described by the propagation vector k = [kx , kx , ½], with kx equal to ¼ for R = Er and Tm or 0.3074 (4) for R = Ho. The magnetic moments are parallel to the c axis for R = Ho or lie within the (001) plane for R = Er and Tm. The obtained magnetic structures are discussed on the basis of symmetry analysis. The rare earth magnetic moments, determined from neutron diffraction data collected at 1.6 K, are 6.5 (1) μB (Er) and 6.09 (4) μB (Tm), while in the incommensurate modulated magnetic structure in Ho2Ni1.78In the amplitude of modulation of the Ho magnetic moment is 7.93 (8) μB. All these values are smaller than those expected for the respective free R 3+ ions. A symmetry analysis of the magnetic structure in Tb2Ni1.78In is also included, as such information is missing from the original paper [Szytuła, Baran, Hoser, Kalychak, Penc & Tyvanchuk (2013). Acta Phys. Pol. A, 124, 994–997]. In addition, the results of magnetometric measurements are reported for Tm2Ni1.78In. The compound shows antiferromagnetic ordering below the Néel temperature of 4.5 K. Its magnetic properties are found to originate from magnetic moments localized solely on the thulium atoms (the nickel atoms remain non-magnetic in Tm2Ni1.78In). The reduction of rare earth magnetic moments in the ordered state in R 2Ni1.78In (R = Tb, Ho, Er and Tm) and the change in direction of the moments indicate the influence of the crystalline electric field (CEF) on the stability of the magnetic order in the investigated compounds.

Magnetic structure of TbBaCo2O5.4 perovskite

2002 ◽  
Vol 17 (4) ◽  
pp. 838-843 ◽  
Author(s):  
D. D. Khalyavin ◽  
I. O. Troyanchuk ◽  
N. V. Kasper ◽  
Q. Huang ◽  
J. W. Lynn ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Wide Temperature Range ◽  
Spontaneous Magnetization ◽  
Magnetic Moments ◽  
Neutron Diffraction Study ◽  
Spin Reorientation ◽  
Magnetic Structures ◽  
Reorientation Process ◽  
Crystal And Magnetic Structures

In accordance with magnetization studies, the fast-cooled TbBaCo2O5.4 is characterized by spontaneous magnetization around 0.18 μB per cobalt ion, which develops below TN = 245 K. The neutron diffraction study of this compound revealed that magnetic moments of Co3+; ions adopting intermediate spine state are ordered antiferromagnetically. Both magnetization and neutron diffraction study showed that there is a spin reorientation process in the wide temperature range. The crystal and magnetic structures are discussed.

scholarly journals Magnetic Option in Jana2006: A Unified Approach by Shubnikov (Super)space Groups

2014 ◽  
Vol 70 (a1) ◽  
pp. C520-C520
Author(s):  
Vaclav Petricek ◽  
Michal Dusek
Keyword(s):  
Parent Phase ◽  
Magnetic Scattering ◽  
Unified Approach ◽  
Space Groups ◽  
Magnetic Structures ◽  
Structure Factors ◽  
Generalized Symmetry ◽  
Magnetic Symmetry ◽  
Two Phases ◽  
Unified Description

The concept of Shubnikov (magnetic) symmetry becomes frequently used for description, solution and refinement of magnetic structures. Its growing importance is connected with the ease of application to various classes of magnetic structures having the translation periodicity identical, commensurate or incommensurate with the nuclear one. Recently generalized superspace approach [1] for incommensurately modulated magnetic structures allows for combination of nuclear and magnetic modulations. This unified description helps fully understand e.g. multiferroic phases. The program Jana2006 (http://jana.fzu.cz) combines the concept of Shubnikov (super)space groups with the representational analysis based on the decomposition of the magnetic configuration space into basis modes, which transform according to different physically irreducible representations (irreps) of the space group of the paramagnetic phase [2]. Moreover, Jana2006 can launch the recently developed program ISODISTORT [3] to obtain similar but more general analysis. The generalized symmetry concept facilitates data processing where symmetry related reflections for single crystal data can be merged and the list of generated reflections for powder data can be reduced to independent ones. Another benefit concerns calculation of magnetic structure factors, stability of refinement and logical way to describe twin domains. Unlike in the Fullproff program [6], Jana2006 can combine the nuclear and magnetic scattering internally without necessity to introduce two phases. It can also calculate magnetic structures with modulated parent phase where the modulation appears before the magnetic phase transition. The lecture shows manifold possibilities how to refine modulated magnetic structures from various experiments. Several recently solved magnetic structures will be presented.

New polarized neutron diffraction setup for precise high-field investigations of magnetic structures up to 8 T at MLZ

2021 ◽  
pp. 1-1
Author(s):  
Vladimir Hutanu ◽  
Henrik Thoma ◽  
Hao Deng ◽  
Georg Brandl ◽  
Alexander Weber ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
High Field ◽  
Magnetic Structures ◽  
Field Investigations ◽  
Polarized Neutron

Interface Electronic And Magnetic Structures Of Layered Fe In Contact With MgO

1991 ◽  
Vol 238 ◽  
Author(s):  
Young Keun Kim ◽  
Michael E. McHenry ◽  
Manuel P. Oliveria ◽  
Mark E. Eberhart
Keyword(s):  
First Principles ◽  
State Of The Art ◽  
Magnetic Moments ◽  
Magnetic Structures ◽  
Consistent Field ◽  
Structure Of Metal ◽  
Metal Ceramic ◽  
Layer Technique ◽  
Self Consistent Field ◽  
Ceramic Interfaces

ABSTRACTA model based on the state-of-the-art, first-principles layer Korringa-Kohn-Rostoker (LKKR) method has proven to be very effective in describing the electronic and magnetic structure of metal/ceramic interfaces. We have performed self-consistent field computations incorporating spin polarization both for Fe/MgO superlattice (bulk technique) and for MgO/Fe/MgO sandwich (layer technique) systems. Muffin-tin potentials were employed for both materials in our computations. Iron layer was embedded in MgO, the host material, to have a [110](100)Fe / [100](100)MgO contact configuration. A large enhancement of magnetic moments has been found at the interface.

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