Structural, Magnetic, and Electrical Properties of Bi1-xLaxMnO3 (x=0.0, 0.1, and 0.2) Solid Solutions

Possible ferromagnetic and ferroelectric orders in ceramic Bi1-xLaxMnO3 (x = 0.0, 0.1, and 0.2) samples prepared under 3-6 GPa pressure have been investigated. Rietveld fits to powder neutron diffraction data show that BiMnO3 and Bi0.9La0.1MnO3 adopt a monoclinic C2/c perovskite superstructure whereas Bi0.8La0.2MnO3 has orthorhombic Pnma symmetry. Both structural analysis and Curie Weiss fits to magnetic susceptibility data show that high spin d(4) Mn3+ is present with no significant Bi deficiency or Mn4+ content apparent. La substitution suppresses the magnetic Curie temperature of the monoclinic phase from 105 K for x 0 to 94 K at x = 0.1, but the x = 0.2 material shows antiferromagnetic order similar to that of LaMnO3. Impedance spectroscopy and dielectric measurements on the x = 0.1 and 0,2 materials show modest bulk permittivity values (45-80) down to 50 K, and there is no strong evidence for ferroelectric behavior. The two samples have thermally activated conductivities with activation energies of 0.21-0.24 eV.