Reference: X. Miao, Y. Gong, L. Caron, Y. You, G. Xu, D. Sheptyakov, P. Manuel, F. Qian, Y. Zhang, F. Xu, N. van Dijk and E. Bruck, Physical Review Materials (2020) 4 104407. DOI: 10.1103/physrevmaterials.4.104407 Atomic positions from: same reference
Parent space group (paramagnetic phase): P63/mmc (#194) Propagation vector: k1 (0, 0, 0)
Transition Temperature: 75 K Experiment Temperature: 1.5 K
Lattice parameters of the magnetic unit cell:
5.2579(1) 4.0697(1) 7.0529(2) 90.00 90.00 90.00 Transformation from parent structure: (-c,-a,a+2b;1/2,1/2,0)
[View matrix form]
Transformation matrix from the setting of the parent structure (ap,bp,cp) to the working setting (a,b,c):
Two magnetic transitions are detected. One at 260K where the moments are aligned along c (parent hexagonal setting) with only irrep mGM2+ active, and a second one at 75K, where the Mn moment adquires an additional component on the hexagonal basal plane.
As the MSG was incorrectly identified as Pnm'a', the structure is described using a standard unit cell for the subgroup of P63/mmc of type Pnma.
FM along a in the setting used.
1k magnetic structure
Two irreps of the hexagonal parent space group are involved as primary, corresponding to the two observed consecutive magnetic transitions.
The second primary irreps is 2-dimensional and is restricted to a special direction.
As the propagation vector of the magnetic arrangement is (0,0,0) and the positional structure is not reported to deviate from the ideal hexagonal positions, the correct MSG of the structure is Cm'c'm (Amc'm' in the setting used).
The unit cell is said in the reference to be constrained by the relation c=sqr(3)*b, but this is inconsistent with the c and b values that are reported. This deviation from hexagonality does not break the C-centered MSG of the structure.
The MSG forces the Co mz to be zero (the second active irrep mGM5+ is only relevant for the Mn sites)