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Magnetic properties of solid solutions between BiCrO 3 and BiGaO 3 with perovskite structures

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ABSTRACT

Magnetic properties of BiCr1−xGaxO3 perovskite-type solid solutions are reported, and a magnetic phase diagram is established. As-synthesized BiCrO3 and BiCr0.9Ga0.1O3 crystallize in a monoclinic (m) C2/c structure. The Néel temperature (TN) decreases from 111 K in BiCrO3 to 98 K in BiCr0.9Ga0.1O3, and spin-reorientation transition temperature increases from 72 K in BiCrO3 to 83 K in BiCr0.9Ga0.1O3. o-BiCr0.9Ga0.1O3 with a PbZrO3-type orthorhombic structure is obtained by heating m-BiCr0.9Ga0.1O3 up to 573 K in air; it shows similar magnetic properties with those of m-BiCr0.9Ga0.1O3. TN of BiCr0.8Ga0.2O3 is 81 K, and TN of BiCr0.7Ga0.3O3 is 63 K. Samples with x = 0.4, 0.5, 0.6 and 0.7 crystallize in a polar R3c structure. Long-range antiferromagnetic order with weak ferromagnetism is observed below TN = 56 K in BiCr0.6Ga0.4O3, TN = 36 K in BiCr0.5Ga0.5O3 and TN = 18 K in BiCr0.4Ga0.6O3. BiCr0.3Ga0.7O3 shows a paramagnetic behaviour because the Cr concentration is below the percolation threshold of 31%.

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Portions of experimental (crosses) and calculated (lines) x-ray powder diffraction patterns of as-synthesized BiCrO3, m-BiCr0.9Ga0.1O3 and m-BiCr0.8Ga0.2O3 measured with the CuKα radiation at room temperature. Possible Bragg positions of the C2/c structure are indicated by tick marks. ‘AB’ means reflections with anisotropic broadening, ‘DS’ means diffuse scattering between some reflections, and ‘RS’ means reflection shifts from their ideal expected positions.
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Figure 1: Portions of experimental (crosses) and calculated (lines) x-ray powder diffraction patterns of as-synthesized BiCrO3, m-BiCr0.9Ga0.1O3 and m-BiCr0.8Ga0.2O3 measured with the CuKα radiation at room temperature. Possible Bragg positions of the C2/c structure are indicated by tick marks. ‘AB’ means reflections with anisotropic broadening, ‘DS’ means diffuse scattering between some reflections, and ‘RS’ means reflection shifts from their ideal expected positions.

Mentions: As-synthesized BiCrO3 and m-BiCr0.9Ga0.1O3 crystallize in the monoclinic (m) C2/c structure. The lattice parameters refined by the Rietveld method are a = 9.4786(4) Å, b = 5.4852(2) Å, c = 9.5824(4) Å and β = 108.587(3)° for BiCrO3 and a = 9.4762(4) Å, b = 5.4899(2) Å, c = 9.5791(4) Å and β = 108.571(3)° for m-BiCr0.9Ga0.1O3. However, both BiCrO3 and BiCr0.9Ga0.1O3 show noticeable anisotropic broadening (AB) of some reflections, the appearance of continuous diffuse scattering (DS) between some reflections, and shifts of some reflections (RS) from their ideal/expected positions (figure 1). Those features are most probably originated from local disorder, the presence of nanodomains [12, 14] and high concentration of domain boundaries and defects; they make the precise Rietveld analysis impossible and result in large variations in refined lattice parameters depending on models used. Similar features are observed in as-synthesized m-BiCr0.8Ga0.2O3 and m-BiCr0.7Ga0.3O3 (figures S1–S3 of the electronic supporting information (ESI)). If those features are modelled as a second perovskite phase (a PbZrO3-related phase with space group Pnma [21]) in the Rietveld analysis, the weight fraction of the second phase is estimated to be about 20% in BiCrO3, 20% in m-BiCr0.9Ga0.1O3, 30% in m-BiCr0.8Ga0.2O3 and 50% in m-BiCr0.7Ga0.3O3 [21]. Electron microscopy and electron diffraction studies showed that the AB, DS and RS features are intrinsic for BiCrO3 and do not originate from the presence of other perovskite phases [12, 14]. They can also be considered as intrinsic in m-BiCr0.9Ga0.1O3 based on the above numbers. However, for unambiguous interpretation of those features in m-BiCr0.8Ga0.2O3 and m-BiCr0.7Ga0.3O3 detailed high-resolution electron microscopy studies are needed.


Magnetic properties of solid solutions between BiCrO 3 and BiGaO 3 with perovskite structures
Portions of experimental (crosses) and calculated (lines) x-ray powder diffraction patterns of as-synthesized BiCrO3, m-BiCr0.9Ga0.1O3 and m-BiCr0.8Ga0.2O3 measured with the CuKα radiation at room temperature. Possible Bragg positions of the C2/c structure are indicated by tick marks. ‘AB’ means reflections with anisotropic broadening, ‘DS’ means diffuse scattering between some reflections, and ‘RS’ means reflection shifts from their ideal expected positions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036460&req=5

Figure 1: Portions of experimental (crosses) and calculated (lines) x-ray powder diffraction patterns of as-synthesized BiCrO3, m-BiCr0.9Ga0.1O3 and m-BiCr0.8Ga0.2O3 measured with the CuKα radiation at room temperature. Possible Bragg positions of the C2/c structure are indicated by tick marks. ‘AB’ means reflections with anisotropic broadening, ‘DS’ means diffuse scattering between some reflections, and ‘RS’ means reflection shifts from their ideal expected positions.
Mentions: As-synthesized BiCrO3 and m-BiCr0.9Ga0.1O3 crystallize in the monoclinic (m) C2/c structure. The lattice parameters refined by the Rietveld method are a = 9.4786(4) Å, b = 5.4852(2) Å, c = 9.5824(4) Å and β = 108.587(3)° for BiCrO3 and a = 9.4762(4) Å, b = 5.4899(2) Å, c = 9.5791(4) Å and β = 108.571(3)° for m-BiCr0.9Ga0.1O3. However, both BiCrO3 and BiCr0.9Ga0.1O3 show noticeable anisotropic broadening (AB) of some reflections, the appearance of continuous diffuse scattering (DS) between some reflections, and shifts of some reflections (RS) from their ideal/expected positions (figure 1). Those features are most probably originated from local disorder, the presence of nanodomains [12, 14] and high concentration of domain boundaries and defects; they make the precise Rietveld analysis impossible and result in large variations in refined lattice parameters depending on models used. Similar features are observed in as-synthesized m-BiCr0.8Ga0.2O3 and m-BiCr0.7Ga0.3O3 (figures S1–S3 of the electronic supporting information (ESI)). If those features are modelled as a second perovskite phase (a PbZrO3-related phase with space group Pnma [21]) in the Rietveld analysis, the weight fraction of the second phase is estimated to be about 20% in BiCrO3, 20% in m-BiCr0.9Ga0.1O3, 30% in m-BiCr0.8Ga0.2O3 and 50% in m-BiCr0.7Ga0.3O3 [21]. Electron microscopy and electron diffraction studies showed that the AB, DS and RS features are intrinsic for BiCrO3 and do not originate from the presence of other perovskite phases [12, 14]. They can also be considered as intrinsic in m-BiCr0.9Ga0.1O3 based on the above numbers. However, for unambiguous interpretation of those features in m-BiCr0.8Ga0.2O3 and m-BiCr0.7Ga0.3O3 detailed high-resolution electron microscopy studies are needed.

View Article: PubMed Central - PubMed

ABSTRACT

Magnetic properties of BiCr1−xGaxO3 perovskite-type solid solutions are reported, and a magnetic phase diagram is established. As-synthesized BiCrO3 and BiCr0.9Ga0.1O3 crystallize in a monoclinic (m) C2/c structure. The Néel temperature (TN) decreases from 111 K in BiCrO3 to 98 K in BiCr0.9Ga0.1O3, and spin-reorientation transition temperature increases from 72 K in BiCrO3 to 83 K in BiCr0.9Ga0.1O3. o-BiCr0.9Ga0.1O3 with a PbZrO3-type orthorhombic structure is obtained by heating m-BiCr0.9Ga0.1O3 up to 573 K in air; it shows similar magnetic properties with those of m-BiCr0.9Ga0.1O3. TN of BiCr0.8Ga0.2O3 is 81 K, and TN of BiCr0.7Ga0.3O3 is 63 K. Samples with x = 0.4, 0.5, 0.6 and 0.7 crystallize in a polar R3c structure. Long-range antiferromagnetic order with weak ferromagnetism is observed below TN = 56 K in BiCr0.6Ga0.4O3, TN = 36 K in BiCr0.5Ga0.5O3 and TN = 18 K in BiCr0.4Ga0.6O3. BiCr0.3Ga0.7O3 shows a paramagnetic behaviour because the Cr concentration is below the percolation threshold of 31%.

No MeSH data available.


Related in: MedlinePlus