MIXED-VALENT TRANSITION METAL OXIDESMas A. Subramanian, Oregon State University, DMR 0804167

• This is an exploratory research project on the identification, synthesis and characterization of new mixed-valent metal oxides with novel functions such as multiferroics. In addition to multiferroic properties (dielectric and magnetic properties), the compounds synthesized under this program are also screened for various phenomena such as superconductivity, magnetoresistance, thermoelectricity, optical properties.

• Complete range of solid-solution between hexagonal YInO3 and YMnO3 were synthesized. We find an enhancement of the magnetocapacitive coupling on dilution with non-magnetic indium ions. The magnitude of this coupling is larger for samples having a greater indium fraction.

• We have discovered that a surprisingly intense bright color samples (blue, green and orange) were obtained when Mn3+, Cu2+, Fe3+ is introduced into the trigonal bipyramidal sites in hexagonal YMO3 oxide. We conclude that the color is a consequence of the crystal field splitting associated with the trigonal bipyramidal coordination. Although unplanned, we expect that our results will lead to the development of earth-abundant, environmentally benign, highly stable inorganic color pigments.

The structures of YMnO3 (left) and LuMgGaO4 (right) as blue trigonal bipyramids (Mn or Mg/Ga), grey Y or Lu and cyan O atoms.

0.1 0.2 0.3

YIn1-xFexO3

Y(Cu0.5Ti0.5)1-xAlxO3

Color pigment samples derived from hexagonal YMO3 structure

• This program is providing training for both undergraduate and graduate students in synthetic materials chemistry, crystal structure analysis and electronic properties. This program also provides these students with the intellectual challenge of understanding the complex behavior of newly synthesized materials and help forge links between chemistry, physics and material science.

• The high school portion of the outreach program is being conducted in conjunction with the successful ASE (Apprenticeships in Science and Engineering) portion of the Saturday Academy Program. So far, five high school students and RUE undergraduate students were participated in this program (2008-10). The ASE organization helped to recruit potential scientists from regional high schools to participate in this program

• Students participating in this research program is gaining experience that will prepare them well for the modern academic and industrial environments.

9th Grader Sam Greydanus (Corvallis High School) testing superconductors he made in PI laboratory during his stay in the summer of 2010. His mentor was Sean Muir (graduate student).

Our discovery of novel color pigments based on trigonal bipyramidal coordination compounds received world-wide interest and featured in many press articles/magazines including NY Times.

MIXED-VALENT TRANSITION METAL OXIDESMas A. Subramanian, Oregon State University, DMR 0804167