Identification of a new type of electronic state in the magnetoresistive orthomanganites

Article Abstract:

Resistivity and thermopower studies of perovskites of composition Ln(sub 1-x)A(sub x)MnO3 at high pressures reveal an unusual origin for their electronic properties. The conduction electrons condense into extended electronic states at temperatures below the Curie temperature and without energy dispersion. The strong linkages between the conduction electrons and cooperative oxygen vibrations along the Mn-O bond axes create the extended electronic states. The colossal magnetoresistance versus temperature relation gives a peak due to Curie temperature shift.

Electron mobility

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Heavy oxygen tips the balance

Article Abstract:

The Curie temperature (T(sub c)) at which lanthanum-based manganites, such as La1-xCaxMnO3+y, become ferromagnetic decreases by more than 20 kelvin if the oxygen atom, 16O, is replaced by 18O. The materials change from insulating to metallic in nature, and from magnetically disordered to ordered at the same temperature. This indicates that the magnetic and electric properties in the manganites are related. The shift in T(sub c) is due to the coupling of charge carriers and Jahn-Teller lattice defects.

Ferromagnetic materials, Transition temperature, Transition temperatures (Thermodynamics)

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Lattice effects in magnetoresistive manganese perovskites

Article Abstract:

It is argued that manganites are important for basic condensed-matter physics due to the interaction between the electrons and lattice vibrations being strong and resulting in a wide range of dramatic physical phenomena. It can also be tuned by variation of chemical composition, magnetic field and temperature, providing an opportunity to study the physics of systems where high density of electrons is strongly linked to phonons.

Lattice dynamics

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