High-pressure synthesis and properties of solid solutions between BiMnO3 and BiScO3

Solid solutions BiMn1-xScxO3 (0 <= x <= 1) were prepared at 6 GPa and 1383-1443 K. Selected area and convergent beam electron diffraction showed that BiMn0.9Sc0.1O3 crystallizes in the centrosymmetric space group C2/c at room temperature. The structure parameters of BiMn0.9Sc0.1O3 were refined by the Rietveld method from laboratory X-ray diffraction data (Z = 8; a = 9.6029(3) angstrom, b = 5.60988(14) angstrom, c = 9.7690(3) angstrom, beta = 108.775(2 degrees) at 293 K). The Mn-O bond lengths suggest that the orbital order present in BiMnO3 at 300 K disappears in BiMn0.9Sc0.1O3. Therefore, the monoclinic-to-monoclinic phase transition observed in BiMnO3 at 474 K and associated with the orbital melting was not detected in BiMn1-xScxO3 for x >= 0.05 down to 133 K. BiMn1-xScxO3 were characterized by dc and ac magnetization, specific heat, and differential scanning calorimetry measurements. The long-range ferromagnetic order seems to survive for x = 0-0.2. For x >= 0.4, the samples showed spin-glass-like features. The Weiss temperature deduced from the fitting of magnetic susceptibilities was positive for all the compositions with x < 1 and decreased monotonically with increasing x. The temperature of the magnetic transitions decreased and the temperature of the structural monoclinic-to-orthorhombic phase transition increased (from 768 K for x = 0 to 840 K for x = 0.3) with increasing x.