CHARACTERISATION OF SUBTLE STRUCTURAL DISTORTIONS IN TRANSITION METAL OXIDES BY HIGH RESOLUTION POWDER DIFFRACTION

摘要

Transition metal oxides are of continuing interest for unusual conducting or magnetic properties such as superconductivity, colossal magnetoresistances, charge ordering, etc. In many cases these phenomena are associated with subtle structural distortions that can be seen and characterised by Rietveld analysis of highly resolved X-ray or neutron powder diffraction data. Usually these involve a change of symmetry, e.g. from orthorhombic to monoclinic as a result of chemical changes in superconducting Tl_2Ba_2CuO_(6+d), or charge ordering in Fe_2OBO_3.