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[20] Ca3Co2O6 is usually described in terms of a hexagonal
cell but the system is actually trigonal. In the primitive
unit cell, the magnetic propagation vector lies on a line of
symmetry (x, x, x) and is transposed to (0, 0, 3x) in the
hexagonal R setting. There is nothing special about x ¼ 1
3
which is inside the Brillouin zone and so the modulation
does not split the magnetic peaks when x � 1
3 .
[21] In our refinement we have fixed at zero the magnetic
moment of the Co I ion because it is now well established
[9,11,15] that the Co I ion is in a LS spin state.
[22] The notation follows Kovalev’s conventions; �1 and �2 are
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D ¼ 2�=FWHM.
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using the procedure implemented in the SXD2001 software.
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Data from TOF Neutron Single-Crystal Diffraction, ISISRAL,
UK (2005).
[27] The crystal used for the SXD experiment was twinned.
The twinning consists of a nonmerohedral reverse-obverse
twin. The data consisted of two components satisfying
the reverse-obverse reflection condition ðh � k þ l ¼
3nÞ=ð�h þ k þ l ¼ 3nÞ with an intensity ratio of 0.473
(2). Fullprof allowed us to use the data from both twin
components in the structural refinement [J. Rodrı´guez-
Carvajal, Physica (Amsterdam) 192B, 55 (1993)].