Novel Properties of Atomically Arranged Perovskites
B. Dabrowski, S. Kolesnik, O. Chmaissem, L. Suescun and J. Mais
Department of Physics, Northern Illinois University, DeKalb, IL 60115, USA
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Received: 04 09 2006;
Perovskites AMO3-δ attain unique electronic, magnetic, ferroelectric, thermoelectric, mixed-conducting, and other functional properties through selection of the A- and M-site ions, their fractions, ionic sizes and valences, spin states, and orbital orderings, as well as the oxygen content and vacancy ordering. We illustrate here our systematic exploration of the effects of composition, temperature, pressure, and oxygen content on the thermodynamic stability and magnetic properties for La1-x-ySrxBayMnO3 manganites. Parameters controlling magnetic transitions are identified through examples of single-valent compounds of RMnO3 (the Mn-O-Mn bond angles that can be equivalently described in terms of the tolerance factor) and Sr1-xCaxMnO3 (the tolerance factor and disorder described in terms of the variance of A-site ion sizes), and the mixed-valent La0.5Sr0.5-yBayMnO3 (the tolerance factor, variance of sizes, and the local strains described in terms of the elongated Mn-O bonds). By using an example of kinetically stable, atomically-ordered layered-perovskites we show that improved useful properties, such as the increase in the Curie temperature TC and enhancement of colossal magneto-resistive effect at room temperature, can be achieved through decreases in structural distortions such as variance of sizes and local strains.
DOI: 10.12693/APhysPolA.111.15
PACS numbers: 75.47.Lx, 75.47.Gk, 61.12.Ld