Magnetic Domains

Whenever the magnetic symmetry of a structure is less than the symmetry of the nuclear structure magnetic domains can occur. Different parts of the crystal conform to one or other of the possible domains. The different types that occur are: configuration domains, 180^o domains, orientation domains and chirality domains.

Configuration domains occur when the propagation vector is not invariant under one or more of the symmetry operations of the space group. Magnetic structure factors are calculated for the configuration domain whose propagation vector is given on the Q PROP card. If magnetic atoms which were equivalent under the full symmetry, are found to be inequivalent with the reduced configuration symmetry CCSL will raise an error. In this case the symmetry cards and atomic positions must be adjusted to conform to the configuration symmetry.

180^o domains occur for all structures for which $\kv =0$; the magnetic structure factors for pairs of 180^o domains are reversed in direction.

Orientation domains occur whenever the magnetic group has symmetry lower than the configurational symmetry i.e. when there are one or more Q NSYM cards.

The subroutines FMCALC and LMCALC calculate magnetic interaction vectors for all the orientation domains and store them in COMMON/QCAL/. They also calculate the mean squared interaction vector for all orientation domains assuming equal populations. This is the quantity used in the MAGLSQ magnetic structure refinement and printed out as $F_m^2$ by the magnetic structure factor program GETMSF.

In cases where chirality domains occur their interaction vectors are also calculated and are included in the averages and in /QCAL/.