Abstract
The spatial symmetry of matter—including finite objects like molecules or atomic clusters, and extended objects like periodic or aperiodic crystals—is described using point groups and space groups. Magnetic point groups and space groups are the simplest extension of this description, to matter whose atomic constituents possess a property that can take one of two possible values, like the “up” or “down” orientations of a magnetic moment, or a spin. Magnetic groups—also known as antisymmetry groups, Shubnikov groups, Heesch groups, Opechowski-Guccione groups, as well as dichromatic, 2-color, or simply black-and-white groups—are here defined, and their structure and notation explained, while providing some pedagogical examples of their enumeration. The resulting magnetic selection rules, or extinctions, in neutron diffraction experiments are discussed. Further extensions to color groups and spin groups are briefly described.
Original language | English |
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Title of host publication | Encyclopedia of Condensed Matter Physics |
Publisher | Elsevier |
Pages | V5:1-V5:10 |
ISBN (Electronic) | 9780323908009 |
ISBN (Print) | 9780323914086 |
DOIs | |
State | Published - 1 Jan 2024 |
Keywords
- Antisymmetry
- Aperiodic crystals
- Belov-Neronova-Smirnova (BNS)
- Black-and-white groups
- Color groups
- Color symmetry
- Crystallography
- Crystals
- Hermann-Mauguin
- Magnetic Bragg peaks
- Magnetic crystals
- Magnetic extinctions
- Magnetic point groups
- Magnetic space groups
- Magnetic symmetry
- Opechowski-Guccione (OG)
- Periodic crystals
- Quasicrystals
- Rokhsar-Wright-Mermin (RWM)
- Shubnikov groups
- Spin groups
- Time reversal