Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100015663/sk1421sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270100015663/sk1421290Ksup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270100015663/sk1421180Ksup3.hkl |
Single crystals YMnO3 were obtained using a flux method by weighing appropriate amounts of Y2O3 and MnO2 with Bi2O3 in a 1:12 ratio (Yakel, 1963). The powders were thoroughly mixed and heated for 48 h at 1523 K in a Pt crucible. The separation of the crystals from the flux has been done by two methods (Bertaut, 1963b). 1) By increasing the temperature to 1723 K and evaporating the Bi2O3 flux, 2) by slowly cooling (50 K/h) through the solidification of the flux. Then the single crystals will segregate on top of the flux. Both methods have been used and the results are equal within the error of the structure determination. We report here only on crystals prepared by slow cooling.
The space group is determined to be P63cm, taking into consideration the unit-cell parameters, statistical analyses of intensity distributions and, where appropriate, systematic extinctions (h-hl: l ≠ 2n; 00 l: l ≠ 2n). Other space groups, that satisfy the same extinction conditions, were discarded during the refinement. Attempts to fit the data on a crystal structure with space group P63/mcm, where unsuccessful. Anisotropic displacement parameters indicated that the atoms at the mirror plane ought to be split in two positions on each side of the mirror plane.
The structure was solved by Patterson methods with SHELXS97 and subsequent difference Fourier maps. The initial co-ordinates were comparable with the isomorphous structure of LuMnO3. The positional and anisotropic displacement parameters were refined.
All the occupied sites were checked for partial occupancy and the Y and the Mn sites were checked for mixed occupancy with Bi: partial occupancy or mixed population did not improve the refinement.
The Flack parameter (Flack, 1983) of an initial refinement indicated that the crystal was twinned. Therefore an inversion twin was added to the structure model. An initial attempt gave a twin fraction of 47 (3)%. We expect a 50%-50% distribution because this yields no net electrical polarization (Rao & Gopalakrishnan, 1997). We fixed the twin fraction at 50(-)%, which had no significant influence on any other parameter.
For both compounds, data collection: CAD4-UNIX software (Enraf-Nonius, 1994); cell refinement: SET4 (de Boer & Duisenberg, 1984); data reduction: HELENA (Spek, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 1994); software used to prepare material for publication: PLATON (Spek, 1990).
MnO3Y | Unit cell parameters (Duisenberg, 1992) and orientation matrix were determined from a least-squares treatment of SET4 (de Boer & Duisenberg, 1984) setting. Reduced cell calculations did not indicate any higher metric lattice symmetry and examination of the final atomic co-ordinates of the structure did not yield extra symmetry elements (Spek, 1988; Le Page 1987, 1988) |
Mr = 191.85 | Dx = 5.135 Mg m−3 |
Hexagonal, P63cm | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 6c -2 | Cell parameters from 22 reflections |
a = 6.1387 (3) Å | θ = 29.8–39.7° |
c = 11.4071 (9) Å | µ = 28.07 mm−1 |
V = 372.27 (4) Å3 | T = 293 K |
Z = 6 | Platelet, black |
F(000) = 528 | 0.15 × 0.15 × 0.02 mm |
Enraf Nonius CAD-4F diffractometer | 658 reflections with I > 2σ(I) |
Radiation source: fine focus sealed Philips Mo tube | Rint = 0.041 |
Perpendicular mounted graphite monochromator | θmax = 40.0°, θmin = 3.6° |
ω/2θ scans | h = 0→11 |
Absorption correction: analytical (Meulenaer & Tompa, 1965) | k = −11→0 |
Tmin = 0.053, Tmax = 0.511 | l = −20→20 |
3385 measured reflections | 3 standard reflections every 180 min |
865 independent reflections | intensity decay: no decay, variation 0.5% |
Refinement on F2 | Primary atom site location: Patterson |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.037 | w = 1/[σ2(Fo2) + (0.0717P)2] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.107 | (Δ/σ)max < 0.001 |
S = 1.12 | Δρmax = 3.11 e Å−3 |
865 reflections | Δρmin = −1.17 e Å−3 |
32 parameters | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
1 restraint | Extinction coefficient: 0.025 (3) |
MnO3Y | Z = 6 |
Mr = 191.85 | Mo Kα radiation |
Hexagonal, P63cm | µ = 28.07 mm−1 |
a = 6.1387 (3) Å | T = 293 K |
c = 11.4071 (9) Å | 0.15 × 0.15 × 0.02 mm |
V = 372.27 (4) Å3 |
Enraf Nonius CAD-4F diffractometer | 658 reflections with I > 2σ(I) |
Absorption correction: analytical (Meulenaer & Tompa, 1965) | Rint = 0.041 |
Tmin = 0.053, Tmax = 0.511 | 3 standard reflections every 180 min |
3385 measured reflections | intensity decay: no decay, variation 0.5% |
865 independent reflections |
R[F2 > 2σ(F2)] = 0.037 | 32 parameters |
wR(F2) = 0.107 | 1 restraint |
S = 1.12 | Δρmax = 3.11 e Å−3 |
865 reflections | Δρmin = −1.17 e Å−3 |
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional co-ordinates. All e.s.d.'s are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
Y1 | 0.00000 | 0.00000 | 0.27122 (12) | 0.0038 (2) | |
Y2 | 0.33333 | 0.66667 | 0.23041 (3) | 0.0041 (1) | |
Mn1 | 0.00000 | 0.3352 (4) | −0.00312 (12) | 0.0058 (2) | |
O1 | 0.00000 | 0.3083 (12) | 0.1596 (7) | 0.0080 (13) | |
O2 | 0.00000 | 0.3587 (10) | −0.1659 (6) | 0.0049 (10) | |
O3 | 0.00000 | 0.00000 | −0.0249 (12) | 0.0053 (16) | |
O4 | 0.33333 | 0.66667 | 0.0155 (11) | 0.0090 (14) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Y1 | 0.0035 (3) | 0.0035 (3) | 0.0044 (4) | 0.0018 (2) | 0.0000 | 0.0000 |
Y2 | 0.0021 (2) | 0.0021 (2) | 0.0081 (3) | 0.0011 (1) | 0.0000 | 0.0000 |
Mn1 | 0.0073 (3) | 0.0060 (3) | 0.0047 (3) | 0.0037 (6) | 0.0000 (2) | 0.0006 (2) |
O1 | 0.008 (3) | 0.010 (2) | 0.0052 (16) | 0.0040 (13) | 0.0000 | −0.0012 (14) |
O2 | 0.005 (2) | 0.0038 (15) | 0.0060 (14) | 0.0023 (10) | 0.0000 | 0.0003 (12) |
O3 | 0.004 (2) | 0.004 (2) | 0.008 (4) | 0.0020 (10) | 0.0000 | 0.0000 |
O4 | 0.008 (2) | 0.008 (2) | 0.011 (3) | 0.0039 (10) | 0.0000 | 0.0000 |
Y1—O1 | 2.281 (7) | Y2—O2viii | 2.300 (4) |
Y1—O2i | 2.316 (6) | Y2—O1ix | 2.275 (5) |
Y1—O3i | 2.326 (14) | Y2—O2v | 2.300 (6) |
Y1—O1ii | 2.281 (7) | Y2—Y2x | 3.5442 (3) |
Y1—O2iii | 2.316 (5) | Y2—Y2xi | 3.5442 (3) |
Y1—O1iv | 2.281 (8) | Y2—Y2xii | 3.5442 (3) |
Y1—O2v | 2.316 (6) | Mn1—O1 | 1.863 (8) |
Y2—O1 | 2.275 (6) | Mn1—O2 | 1.862 (7) |
Y2—O2 | 2.300 (4) | Mn1—O3 | 2.073 (3) |
Y2—O4vi | 2.451 (13) | Mn1—O4 | 2.052 (3) |
Y2—O1vii | 2.275 (8) | Mn1—O4x | 2.052 (4) |
O1—Y1—O2i | 77.20 (17) | Y2xii—Y2—O1vii | 86.65 (16) |
O1—Y1—O3i | 123.93 (19) | O1ix—Y2—O2viii | 77.6 (2) |
O1—Y1—O1ii | 91.9 (2) | O2viii—Y2—O2v | 95.9 (2) |
O1—Y1—O2iii | 164.1 (3) | Y2x—Y2—O2viii | 39.61 (14) |
O1—Y1—O1iv | 91.9 (2) | Y2xi—Y2—O2viii | 135.38 (14) |
O1—Y1—O2v | 77.2 (2) | Y2xii—Y2—O2viii | 93.36 (13) |
O2i—Y1—O3i | 71.96 (17) | O1ix—Y2—O2v | 169.8 (3) |
O1ii—Y1—O2i | 77.2 (2) | Y2x—Y2—O1ix | 86.65 (16) |
O2i—Y1—O2iii | 110.86 (14) | Y2xi—Y2—O1ix | 146.85 (18) |
O1iv—Y1—O2i | 164.1 (3) | Y2xii—Y2—O1ix | 38.85 (15) |
O2i—Y1—O2v | 110.86 (19) | Y2x—Y2—O2v | 93.36 (16) |
O1ii—Y1—O3i | 123.9 (2) | Y2xi—Y2—O2v | 39.61 (17) |
O2iii—Y1—O3i | 71.96 (17) | Y2xii—Y2—O2v | 135.38 (15) |
O1iv—Y1—O3i | 123.9 (2) | Y2x—Y2—Y2xi | 120.00 (1) |
O2v—Y1—O3i | 71.96 (17) | Y2x—Y2—Y2xii | 120.00 (1) |
O1ii—Y1—O2iii | 77.2 (2) | Y2xi—Y2—Y2xii | 120.00 (1) |
O1ii—Y1—O1iv | 91.9 (2) | O1—Mn1—O2 | 179.4 (3) |
O1ii—Y1—O2v | 164.1 (3) | O1—Mn1—O3 | 91.8 (4) |
O1iv—Y1—O2iii | 77.20 (16) | O1—Mn1—O4 | 86.6 (4) |
O2iii—Y1—O2v | 110.9 (2) | O1—Mn1—O4x | 86.6 (4) |
O1iv—Y1—O2v | 77.2 (2) | O2—Mn1—O3 | 87.6 (4) |
O1—Y2—O4 | 69.2 (2) | O2—Mn1—O4 | 93.7 (4) |
O1—Y2—O2vi | 169.8 (2) | O2—Mn1—O4x | 93.7 (4) |
O1—Y2—O1vii | 108.1 (2) | O3—Mn1—O4 | 120.13 (16) |
O1—Y2—O2viii | 77.1 (2) | O3—Mn1—O4x | 120.13 (12) |
O1—Y2—O1ix | 108.1 (2) | O4—Mn1—O4x | 119.49 (15) |
O1—Y2—O2v | 77.6 (2) | Y1—O1—Y2 | 103.4 (3) |
Y2x—Y2—O1 | 38.85 (13) | Y1—O1—Mn1 | 129.0 (3) |
Y2xi—Y2—O1 | 86.65 (11) | Y1—O1—Y2x | 103.4 (3) |
Y2xii—Y2—O1 | 146.85 (15) | Y2—O1—Mn1 | 107.9 (3) |
O2vi—Y2—O4 | 120.94 (15) | Y2—O1—Y2x | 102.3 (3) |
O1vii—Y2—O4 | 69.2 (2) | Y2x—O1—Mn1 | 107.9 (3) |
O2viii—Y2—O4 | 120.94 (15) | Y1xiii—O2—Mn1 | 103.6 (2) |
O1ix—Y2—O4 | 69.21 (19) | Y2xiii—O2—Mn1 | 122.8 (2) |
O2v—Y2—O4 | 120.94 (16) | Y2xiv—O2—Mn1 | 122.8 (3) |
Y2x—Y2—O4 | 90.00 (1) | Y1xiii—O2—Y2xiii | 101.5 (2) |
Y2xi—Y2—O4 | 90.00 (1) | Y1xiii—O2—Y2xiv | 101.5 (2) |
Y2xii—Y2—O4 | 90.00 (1) | Y2xiii—O2—Y2xiv | 100.8 (2) |
O1vii—Y2—O2vi | 77.6 (2) | Y1xiii—O3—Mn1 | 96.9 (4) |
O2vi—Y2—O2viii | 95.9 (2) | Mn1—O3—Mn1ii | 118.58 (19) |
O1ix—Y2—O2vi | 77.1 (2) | Mn1—O3—Mn1iv | 118.58 (19) |
O2vi—Y2—O2v | 95.9 (2) | Y1xiii—O3—Mn1ii | 96.9 (4) |
Y2x—Y2—O2vi | 135.38 (16) | Y1xiii—O3—Mn1iv | 96.9 (4) |
Y2xi—Y2—O2vi | 93.36 (14) | Mn1ii—O3—Mn1iv | 118.58 (19) |
Y2xii—Y2—O2vi | 39.61 (13) | Y2—O4—Mn1 | 95.9 (4) |
O1vii—Y2—O2viii | 169.8 (3) | Y2—O4—Mn1vii | 95.9 (4) |
O1vii—Y2—O1ix | 108.1 (3) | Y2—O4—Mn1ix | 95.9 (4) |
O1vii—Y2—O2v | 77.1 (2) | Mn1—O4—Mn1vii | 118.94 (17) |
Y2x—Y2—O1vii | 146.85 (18) | Mn1—O4—Mn1ix | 118.94 (18) |
Y2xi—Y2—O1vii | 38.85 (17) | Mn1vii—O4—Mn1ix | 118.94 (18) |
O4—Y2—O1—Y1 | 134.7 (2) | O4—Mn1—O1—Y1 | −120.1 (3) |
O4—Y2—O1—Mn1 | −4.45 (17) | O4—Mn1—O1—Y2 | 4.98 (19) |
O1—Y2—O4—Mn1 | 3.87 (15) | O1—Mn1—O4—Y2 | −4.42 (17) |
O3—Mn1—O1—Y1 | 0.0 (3) | O2—Mn1—O4—Y2 | 176.13 (15) |
O3—Mn1—O1—Y2 | 125.06 (17) | O3—Mn1—O4—Y2 | −94.5 (5) |
Symmetry codes: (i) x−y, x, z+1/2; (ii) −y, x−y, z; (iii) −x, −y, z+1/2; (iv) −x+y, −x, z; (v) y, −x+y, z+1/2; (vi) x−y+1, x+1, z+1/2; (vii) −y+1, x−y+1, z; (viii) −x, −y+1, z+1/2; (ix) −x+y, −x+1, z; (x) y−1, x, z; (xi) y, x, z; (xii) y, x+1, z; (xiii) x−y, x, z−1/2; (xiv) −x+y, y, z−1/2. |
MnO3Y | Unit cell parameters (Duisenberg, 1992) and orientation matrix were determined from a least-squares treatment of SET4 (de Boer & Duisenberg, 1984) setting. Reduced cell calculations did not indicate any higher metric lattice symmetry and examination of the final atomic co-ordinates of the structure did not yield extra symmetry elements (Spek, 1988; Le Page 1987, 1988) |
Mr = 191.85 | Dx = 5.151 Mg m−3 |
Hexagonal, P63cm | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 6c -2 | Cell parameters from 22 reflections |
a = 6.1277 (5) Å | θ = 29.8–39.8° |
c = 11.411 (1) Å | µ = 28.16 mm−1 |
V = 371.06 (5) Å3 | T = 180 K |
Z = 6 | Platelet, black |
F(000) = 528 | 0.15 × 0.02 × 0.02 mm |
Enraf Nonius CAD-4F diffractometer | 658 reflections with I > 2σ(I) |
Radiation source: fine focus sealed Philips Mo tube | Rint = 0.040 |
Perpendicular mounted graphite monochromator | θmax = 39.9°, θmin = 3.6° |
ω/2θ scans | h = 0→11 |
Absorption correction: analytical (Meulenaer & Tompa, 1965) | k = −11→0 |
Tmin = 0.065, Tmax = 0.510 | l = −18→20 |
3336 measured reflections | 3 standard reflections every 180 min |
853 independent reflections | intensity decay: no decay, variation 0.5% |
Refinement on F2 | Primary atom site location: Patterson |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.037 | w = 1/[σ2(Fo2) + (0.0717P)2] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.109 | (Δ/σ)max < 0.001 |
S = 1.09 | Δρmax = 2.31 e Å−3 |
853 reflections | Δρmin = −1.36 e Å−3 |
32 parameters | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
1 restraint | Extinction coefficient: 0.018 (2) |
MnO3Y | Z = 6 |
Mr = 191.85 | Mo Kα radiation |
Hexagonal, P63cm | µ = 28.16 mm−1 |
a = 6.1277 (5) Å | T = 180 K |
c = 11.411 (1) Å | 0.15 × 0.02 × 0.02 mm |
V = 371.06 (5) Å3 |
Enraf Nonius CAD-4F diffractometer | 658 reflections with I > 2σ(I) |
Absorption correction: analytical (Meulenaer & Tompa, 1965) | Rint = 0.040 |
Tmin = 0.065, Tmax = 0.510 | 3 standard reflections every 180 min |
3336 measured reflections | intensity decay: no decay, variation 0.5% |
853 independent reflections |
R[F2 > 2σ(F2)] = 0.037 | 32 parameters |
wR(F2) = 0.109 | 1 restraint |
S = 1.09 | Δρmax = 2.31 e Å−3 |
853 reflections | Δρmin = −1.36 e Å−3 |
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional co-ordinates. All e.s.d.'s are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
Y1 | 0.00000 | 0.00000 | 0.27175 (12) | 0.0024 (2) | |
Y2 | 0.33333 | −0.33333 | 0.22989 (4) | 0.0024 (1) | |
Mn1 | 0.3344 (4) | 0.0000 (8) | −0.00312 (12) | 0.0041 (2) | |
O1 | 0.3090 (12) | 0.00000 | 0.1596 (7) | 0.0036 (11) | |
O2 | 0.3610 (11) | 0.00000 | −0.1660 (6) | 0.0051 (13) | |
O3 | 0.00000 | 0.00000 | −0.0236 (15) | 0.0056 (16) | |
O4 | 0.33333 | −0.33333 | 0.0168 (11) | 0.0050 (11) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Y1 | 0.0021 (3) | 0.0021 (3) | 0.0030 (4) | 0.0010 (2) | 0.0000 | 0.0000 |
Y2 | 0.0010 (2) | 0.0010 (2) | 0.0051 (3) | 0.0005 (1) | 0.0000 | 0.0000 |
Mn1 | 0.0036 (3) | 0.0053 (3) | 0.0039 (3) | 0.0026 (6) | 0.0003 (2) | 0.0000 (2) |
O1 | 0.0046 (18) | 0.001 (2) | 0.0042 (17) | 0.0006 (10) | −0.0023 (13) | 0.0000 |
O2 | 0.0045 (16) | 0.007 (3) | 0.0046 (16) | 0.0034 (13) | 0.0011 (13) | 0.0000 |
O3 | 0.005 (2) | 0.005 (2) | 0.007 (4) | 0.0026 (12) | 0.0000 | 0.0000 |
O4 | 0.0031 (18) | 0.0031 (18) | 0.009 (2) | 0.0016 (9) | 0.0000 | 0.0000 |
Y1—O1 | 2.285 (8) | Y2—O2viii | 2.295 (4) |
Y1—O2i | 2.323 (6) | Y2—O1ix | 2.268 (8) |
Y1—O3i | 2.335 (17) | Y2—O2v | 2.295 (5) |
Y1—O1ii | 2.285 (7) | Y2—Y2x | 3.5378 (3) |
Y1—O2iii | 2.323 (7) | Y2—Y2xi | 3.5378 (3) |
Y1—O1iv | 2.285 (7) | Y2—Y2xii | 3.5378 (3) |
Y1—O2v | 2.323 (6) | Mn1—O1 | 1.863 (8) |
Y2—O1 | 2.268 (5) | Mn1—O2 | 1.866 (7) |
Y2—O4 | 2.432 (13) | Mn1—O3 | 2.062 (4) |
Y2—O2vi | 2.295 (7) | Mn1—O4 | 2.052 (3) |
Y2—O1vii | 2.268 (6) | Mn1—O4xii | 2.052 (3) |
O1—Y1—O2i | 77.1 (2) | Y2xii—Y2—O1vii | 146.83 (15) |
O1—Y1—O3i | 124.1 (2) | O1ix—Y2—O2viii | 78.0 (2) |
O1—Y1—O1ii | 91.7 (2) | O2viii—Y2—O2v | 95.6 (2) |
O1—Y1—O2iii | 163.7 (3) | Y2x—Y2—O2viii | 134.98 (17) |
O1—Y1—O1iv | 91.7 (2) | Y2xi—Y2—O2viii | 93.67 (15) |
O1—Y1—O2v | 77.10 (17) | Y2xii—Y2—O2viii | 39.57 (13) |
O2i—Y1—O3i | 72.20 (17) | O1ix—Y2—O2v | 169.5 (3) |
O1ii—Y1—O2i | 77.1 (2) | Y2x—Y2—O1ix | 146.83 (18) |
O2i—Y1—O2iii | 111.1 (2) | Y2xi—Y2—O1ix | 38.73 (17) |
O1iv—Y1—O2i | 163.7 (3) | Y2xii—Y2—O1ix | 86.74 (16) |
O2i—Y1—O2v | 111.1 (2) | Y2x—Y2—O2v | 39.57 (15) |
O1ii—Y1—O3i | 124.05 (19) | Y2xi—Y2—O2v | 134.98 (15) |
O2iii—Y1—O3i | 72.20 (17) | Y2xii—Y2—O2v | 93.67 (15) |
O1iv—Y1—O3i | 124.05 (19) | Y2x—Y2—Y2xi | 120.00 (1) |
O2v—Y1—O3i | 72.20 (17) | Y2x—Y2—Y2xii | 120.00 (1) |
O1ii—Y1—O2iii | 77.10 (17) | Y2xi—Y2—Y2xii | 120.00 (1) |
O1ii—Y1—O1iv | 91.7 (2) | O1—Mn1—O2 | 179.8 (4) |
O1ii—Y1—O2v | 163.7 (3) | O1—Mn1—O3 | 91.7 (5) |
O1iv—Y1—O2iii | 77.1 (2) | O1—Mn1—O4 | 86.0 (4) |
O2iii—Y1—O2v | 111.09 (14) | O1—Mn1—O4xii | 86.0 (4) |
O1iv—Y1—O2v | 77.1 (2) | O2—Mn1—O3 | 88.5 (5) |
O1—Y2—O4 | 69.29 (19) | O2—Mn1—O4 | 93.9 (4) |
O1—Y2—O2vi | 169.5 (3) | O2—Mn1—O4xii | 93.9 (4) |
O1—Y2—O1vii | 108.2 (2) | O3—Mn1—O4 | 120.26 (16) |
O1—Y2—O2viii | 76.9 (2) | O3—Mn1—O4xii | 120.26 (16) |
O1—Y2—O1ix | 108.2 (3) | O4—Mn1—O4xii | 119.10 (17) |
O1—Y2—O2v | 78.0 (2) | Y1—O1—Y2 | 103.3 (2) |
Y2x—Y2—O1 | 86.74 (16) | Y1—O1—Mn1 | 128.8 (4) |
Y2xi—Y2—O1 | 146.83 (18) | Y1—O1—Y2xii | 103.3 (2) |
Y2xii—Y2—O1 | 38.73 (15) | Y2—O1—Mn1 | 108.0 (3) |
O2vi—Y2—O4 | 121.18 (17) | Y2—O1—Y2xii | 102.5 (3) |
O1vii—Y2—O4 | 69.3 (2) | Y2xii—O1—Mn1 | 108.0 (3) |
O2viii—Y2—O4 | 121.18 (15) | Y1xiii—O2—Mn1 | 102.8 (3) |
O1ix—Y2—O4 | 69.3 (2) | Y2xiii—O2—Mn1 | 123.2 (2) |
O2v—Y2—O4 | 121.18 (15) | Y2xiv—O2—Mn1 | 123.2 (2) |
Y2x—Y2—O4 | 90.00 (1) | Y1xiii—O2—Y2xiii | 101.3 (2) |
Y2xi—Y2—O4 | 90.00 (1) | Y1xiii—O2—Y2xiv | 101.3 (2) |
Y2xii—Y2—O4 | 90.00 (1) | Y2xiii—O2—Y2xiv | 100.9 (3) |
O1vii—Y2—O2vi | 78.0 (2) | Y1xiii—O3—Mn1 | 96.5 (5) |
O2vi—Y2—O2viii | 95.6 (2) | Mn1—O3—Mn1ii | 118.7 (2) |
O1ix—Y2—O2vi | 76.9 (3) | Mn1—O3—Mn1iv | 118.7 (2) |
O2vi—Y2—O2v | 95.6 (2) | Y1xiii—O3—Mn1ii | 96.5 (5) |
Y2x—Y2—O2vi | 93.67 (18) | Y1xiii—O3—Mn1iv | 96.5 (5) |
Y2xi—Y2—O2vi | 39.57 (18) | Mn1ii—O3—Mn1iv | 118.7 (2) |
Y2xii—Y2—O2vi | 134.98 (16) | Y2—O4—Mn1 | 96.4 (3) |
O1vii—Y2—O2viii | 169.5 (2) | Y2—O4—Mn1vii | 96.4 (3) |
O1vii—Y2—O1ix | 108.2 (2) | Y2—O4—Mn1ix | 96.4 (3) |
O1vii—Y2—O2v | 76.9 (2) | Mn1—O4—Mn1vii | 118.79 (19) |
Y2x—Y2—O1vii | 38.73 (13) | Mn1—O4—Mn1ix | 118.79 (17) |
Y2xi—Y2—O1vii | 86.74 (11) | Mn1vii—O4—Mn1ix | 118.79 (18) |
O4—Y2—O1—Y1 | 134.8 (2) | O4—Mn1—O1—Y1 | −120.22 (8) |
O4—Y2—O1—Mn1 | −4.2 (2) | O4—Mn1—O1—Y2 | 4.7 (2) |
O1—Y2—O4—Mn1 | 3.65 (19) | O1—Mn1—O4—Y2 | −4.2 (2) |
O3—Mn1—O1—Y1 | 0.00 (17) | O2—Mn1—O4—Y2 | 175.6 (2) |
O3—Mn1—O1—Y2 | 124.9 (2) | O3—Mn1—O4—Y2 | −93.8 (6) |
Symmetry codes: (i) x−y, x, z+1/2; (ii) −y, x−y, z; (iii) −x, −y, z+1/2; (iv) −x+y, −x, z; (v) y, −x+y, z+1/2; (vi) x−y, x−1, z+1/2; (vii) −y, x−y−1, z; (viii) −x+1, −y, z+1/2; (ix) −x+y+1, −x, z; (x) y, x−1, z; (xi) y+1, x−1, z; (xii) y+1, x, z; (xiii) x−y, x, z−1/2; (xiv) −x+y+1, y, z−1/2. |
Experimental details
(290K) | (180K) | |
Crystal data | ||
Chemical formula | MnO3Y | MnO3Y |
Mr | 191.85 | 191.85 |
Crystal system, space group | Hexagonal, P63cm | Hexagonal, P63cm |
Temperature (K) | 293 | 180 |
a, c (Å) | 6.1387 (3), 11.4071 (9) | 6.1277 (5), 11.411 (1) |
V (Å3) | 372.27 (4) | 371.06 (5) |
Z | 6 | 6 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 28.07 | 28.16 |
Crystal size (mm) | 0.15 × 0.15 × 0.02 | 0.15 × 0.02 × 0.02 |
Data collection | ||
Diffractometer | Enraf Nonius CAD-4F diffractometer | Enraf Nonius CAD-4F diffractometer |
Absorption correction | Analytical (Meulenaer & Tompa, 1965) | Analytical (Meulenaer & Tompa, 1965) |
Tmin, Tmax | 0.053, 0.511 | 0.065, 0.510 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3385, 865, 658 | 3336, 853, 658 |
Rint | 0.041 | 0.040 |
(sin θ/λ)max (Å−1) | 0.903 | 0.903 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.037, 0.107, 1.12 | 0.037, 0.109, 1.09 |
No. of reflections | 865 | 853 |
No. of parameters | 32 | 32 |
No. of restraints | 1 | 1 |
Δρmax, Δρmin (e Å−3) | 3.11, −1.17 | 2.31, −1.36 |
Computer programs: CAD4-UNIX software (Enraf-Nonius, 1994), SET4 (de Boer & Duisenberg, 1984), HELENA (Spek, 1997), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 1994), PLATON (Spek, 1990).
Y1—O1 | 2.281 (7) | Y2—Y2iii | 3.5442 (3) |
Y1—O2i | 2.316 (6) | Mn1—O1 | 1.863 (8) |
Y1—O3i | 2.326 (14) | Mn1—O2 | 1.862 (7) |
Y2—O1 | 2.275 (6) | Mn1—O3 | 2.073 (3) |
Y2—O2 | 2.300 (4) | Mn1—O4 | 2.052 (3) |
Y2—O4ii | 2.451 (13) |
Symmetry codes: (i) x−y, x, z+1/2; (ii) x−y+1, x+1, z+1/2; (iii) y−1, x, z. |
The compounds LnMnO3, with Ln a lanthanide, have attracted much interest in two different fields of materials science. The large ionic radius lanthanides, La, Ce—Dy, crystallize in a distorted orthorhombic perovskite structure (Yakel, 1955). The compounds have recently gained enormous interest because of the colossal magnetoresistance effect, i.e. a metal-insulator transition that changes the conductivity by many orders of magnitude at the Curie temperature (Ramirez, 1997). The Mn is octahedrally coordinated by O. The octahedra form a corner-shared three-dimensional network. The small ionic radius lanthanides, Ho—Lu, crystallize in a hexagonal structure (Yakel et al., 1963). Here, the Mn ions are co-ordinated by a trigonal bipyramid of O, forming a pseudo-layered structure by corner sharing of the trigonal basal plane O atoms. These compounds are of interest because of the combination of ferroelectric and magnetic ordering (Smolenskii & Bokov, 1964). The intermediate ionic radius of Y allows both crystal structures; under ambient conditions, the hexagonal structure is obtained. But the orthorhombic structure can be stabilized by either low temperature (Brinks et al., 1997), or high pressure synthesis (Waintal & Chevanas, 1967), or epitaxic thin film growth (Salvador et al., 1998).
The magnetic properties of hexagonal YMnO3 were reported by Bertaut & Mercier (1963) from powder neutron diffraction experiments. They found a frustrated triangular basal plane spin structure at 4.2 K. The measurements allowed two stacking sequences for the basal planes spin structure, only one of which allows a ferromagnetic canting. Because ceramic samples showed a ferromagnetic component in the magnetization below 45 K, this stacking sequence was favoured. However, this conclusion was withdrawn when it was realised that the ferromagnetic component originates from small amounts of the impurity phase Mn3O4 (Bertaut et al., 1965). Despite various reports on single-crystal growth of YMnO3 (Yakel et al., 1963; Bertaut et al., 1963), we could find in the open literature neither the crystallographic structure determination nor the temperature-dependent magnetization of phase-pure samples. Here we report the details of the refinement of the crystal structure. We will show in a separate publication the magnetic behaviour; these single crystals exhibit an antiferromagnetic anomaly at TN = 75 K, and a large magnetic anisotropy as expected for this crystal structure (Van Aken et al., 2000).
In table 2, the metal-oxygen bond lengths are given. Both yttrium positions and the manganese position have unusual oxygen environments. In the centrosymmetric, high temperature phase, Ts = 1283 K, (Łukaszewicz & Karut-Kalicinska, 1977) the single yttrium has an eightfold co-ordination, in the form of a bicapped trigonal antiprism. In the noncentrosymmetric structure, the capping O atoms are displaced with respect to the yttrium in such a way that the Y—O bond length changes from twice 2.7 Å to 2.4 Å and 3.3 Å. Manganese is surrounded by five O atoms in a trigonal bipyramidal way. Striking is the difference in bond length between in-plane and out-of-plane bonds, respectively ≈ 2.05 Å and ≈ 1.86 Å. The origin of this difference is the orbital occupation given by the crystal-field splitting of Mn3+. The three-dimensional states split in a trigonal bipyramidal field according to the magnetic quantum number (Van Aken et al., 2000). This yields an empty z2 orbital, which is in agreement with the shorter Mn—O distances along the c axis, than in the ab plane. It can easily be shown that the 3 d4 ground state is non-degenerate and thus not Jahn-Teller active.
The non-equivalent Mn—O atomic distances, both within the basal plane and to the apices, have smaller differences than in isomorphous LuMnO3. Nevertheless, the Mn ion is not located in the centre of the trigonal bipyramid. It is both displaced in the a-b basal plane, and along the c axis. The three Mn displacement vectors within the basal plane cancel each other in a triangular fashion. The displacement along the c axis is the same for all Mn ions in the unit cell. Furthermore, the yttrium ions are also non-symmetrically surrounded by the O atoms. This means that YMnO3 is ferroelectric and an ordering temperature of ≈920 K has been reported (Smolenskii & Chupis, 1982). The macroscopic electric polarization is cancelled by an inversion twin. The origin of the ferroelectricity is not known at the moment. One possibility could be the fact that this hexagonal YMnO3 is less dense than the perovskite YMnO3. This could mean that there is some excess volume in the centrosymmetric HT phase. The excess volume can be reduced by rotating or deforming the oxygen polyhedra around the metal ions. This could lead to the disappearance of the inversion centre.
We conclude that YMnO3 is ferroelectric with a frustrated displacement pattern. Both the Y and the Mn ions are shifted along the c axis. The electric polarization is cancelled by inversion twinning. Both methods for synthesis result in single crystals of the same quality.