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(Mn,Co)WO4 compounds are regarded as reference spin-induced multiferroics. A comparative study is presented here, within the magnetic symmetry framework, of the incommensurate magnetic orders responsible for the ferroelectric phases of (i) MnWO4 under a magnetic field (H || b) and (ii) Mn0.90Co0.10WO4 in the absence of an external field. On the one hand, although these two ferroelectric phases are stabilized under different external physical conditions, both present the same Xc1′(α0γ)ss magnetic symmetry and practically the same modulation vector. The magnetic ordering in both phases is an elliptical helix with the magnetic moments (as the polarization vector, P) perpendicular to the b axis, although in most of the ferroelectric compositions of the (Mn,Co)WO4 family the spins rotate in planes containing b (and have P || b). On the other hand, the anisotropy of the resulting magnetic modulations is extraordinarily different in the two phases. This is described and explained in the light of the different anisotropies of Co and Mn ions.
Supporting information
CCDC references: 1458113; 1458114
Crystal data top
Co0.1Mn0.9O4W | β = 90.912° |
Mr = 303.7 | V = 275.13 Å3 |
Monoclinic, Xc.1(α0γ)ss | Z = 2 |
q = -0.222000a* + 0.472000c* | F(000) = 525 |
a = 4.8068 Å | Dx = 3.787 Mg m−3 |
b = 11.488 Å | Neutrons radiation, λ = 1.2832 Å |
c = 4.983 Å | T = 2 K |
Data collection top
649 measured reflections | θmax = 54.1°, θmin = 5.0° |
367 independent reflections | h = −5→5 |
300 reflections with I > 3σ(I) | k = −13→13 |
Rint = 0.028 | l = −2→1 |
Refinement top
Refinement on F | 0 restraints |
R[F2 > 2σ(F2)] = 0.054 | 8 constraints |
wR(F2) = 0.063 | Weighting scheme based on measured s.u.'s w = 1/(σ2(F) + 0.0001F2) |
S = 2.98 | (Δ/σ)max = 0.038 |
367 reflections | Absolute structure: 121 of Friedel pairs used in the refinement |
4 parameters | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Mn1 | 0.5 | 0.3426 | 0.25 | 0* | 0.906 |
Co1 | 0.5 | 0.3426 | 0.25 | 0* | 0.094 |
W1 | 0 | 0.0909 | 0.25 | 0* | |
O1_1 | 0.2111 | 0.05105 | 0.941 | 0* | |
O1_2 | −0.2111 | −0.05105 | −0.941 | 0* | |
O2_1 | 0.2512 | 0.1874 | 0.393 | 0* | |
O2_2 | −0.2512 | −0.1874 | −0.393 | 0* | |
Crystal data top
Co0.1Mn0.9O4W | β = 90.912° |
Mr = 303.7 | V = 275.13 Å3 |
Monoclinic, Xc.1(α0γ)ss | Z = 2 |
q = -0.222000a* + 0.472000c* | F(000) = 525 |
a = 4.8068 Å | Dx = 3.787 Mg m−3 |
b = 11.488 Å | Neutrons radiation, λ = 1.2832 Å |
c = 4.983 Å | T = 9 K |
Data collection top
641 measured reflections | θmax = 55.0°, θmin = 5.0° |
362 independent reflections | h = −5→5 |
280 reflections with I > 3σ(I) | k = −13→13 |
Rint = 0.033 | l = −2→1 |
Refinement top
Refinement on F | 0 restraints |
R[F2 > 2σ(F2)] = 0.061 | 8 constraints |
wR(F2) = 0.063 | Weighting scheme based on measured s.u.'s w = 1/(σ2(F) + 0.0001F2) |
S = 2.79 | (Δ/σ)max = 0.045 |
362 reflections | Absolute structure: 116 of Friedel pairs used in the refinement |
4 parameters | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Mn1 | 0.5 | 0.34233 | 0.25 | 0* | 0.906 |
Co1 | 0.5 | 0.34233 | 0.25 | 0* | 0.094 |
W1 | 0 | 0.0901 | 0.25 | 0* | |
O1_1 | 0.21142 | 0.05145 | 0.941 | 0* | |
O1_2 | −0.21142 | −0.05145 | −0.941 | 0* | |
O2_1 | 0.2515 | 0.187535 | 0.3941 | 0* | |
O2_2 | −0.2515 | −0.187535 | −0.3941 | 0* | |
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