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Despite numerous attempts to explain the phenomenon of transport and magnetoresistance in manganites based on Jahn–Teller phonon coupling and double exchange mechanisms, satisfactory results could not be reached. The small polaron transport mechanism, based on the valence exchange arising from Madelung energy, is shown to account for the resistivity and magnetoresistance of the doped manganite La2/3Ca1/3MnO3 in the ferromagnetic range. The transport equation for the correlated polaron based on the Holstein Hamiltonian shows the well known transition from the low temperature band to the localized polaron hopping conductivity at high temperature in agreement with experiment. The present attempt is to demonstrate that the complexity of the problem that involves the interplay between the spin and charge order on one hand and itinerant and localized behavior on the other for a simple ferromagnetic metal system of manganites is best described by the correlated small polaron model leaving the more complicated systems for future studies. [ABSTRACT FROM AUTHOR]

Despite numerous attempts to explain the phenomenon of transport and magnetoresistance in manganites based on Jahn–Teller phonon coupling and double exchange mechanisms, satisfactory results could not be reached. The small polaron transport mechanism, based on the valence exchange arising from Madelung energy, is shown to account for the resistivity and magnetoresistance of the doped manganite La2/3Ca1/3MnO3 in the ferromagnetic range. The transport equation for the correlated polaron based on the Holstein Hamiltonian shows the well known transition from the low temperature band to the localized polaron hopping conductivity at high temperature in agreement with experiment. The present attempt is to demonstrate that the complexity of the problem that involves the interplay between the spin and charge order on one hand and itinerant and localized behavior on the other for a simple ferromagnetic metal system of manganites is best described by the correlated small polaron model leaving the more complicated systems for future studies. [ABSTRACT FROM AUTHOR]

Investigates the magnetization and linewidth for liquid-phase-epitaxially grown thin films of europium-yttrium-iron-gallium-oxygen. Substitution of gallium on iron sublattices and its effect on temperature dependence; Theory of ferromagnetic resonance in rare-earth iron garnets; Relaxation of mechanism in thin films with large uniaxial anisotropy.

The transport behavior of La1-xSrxMnO3 in the antiferromagnetic insulator, ferromagnetic insulator, and ferromagnetic metallic phases is shown to follow from the correlated polaron mechanism and a single transport equation accounts for the temperature dependence of resistivity for 0≤x≤0.40 in the 0–400 K range. In the low temperature range zero-point lattice vibration plays a dominant role in the transport in the metallic phase. [ABSTRACT FROM AUTHOR]

The magnetic and electrical transport properties of La0.67Ca0.33MnO3 (LCMO): xSiCN (x=0–40 vol %) composites, synthesized by mechanical mixing of citrate gel derived LCMO and polymer derived ceramics SiCN, have been investigated as a function of composition. The ability of SiCN to behave as a sintering additive leads to interesting magnetic and electrical properties. Si+4, being strongly favored for tetrahedral coordination, cannot enter the perovskite lattice. Saturation moment, MS of 68 emu/gm at 5 K and at 5 kOe field of pure LCMO shifts to 79 emu/gm in the sample with x=0.05 and then decreases monotonically as x increases further. The lower MS, TC and high electrical resistivity of the sample with x=0, compared to those which have been reported in the literature, is due to small particle size in nm range. SiCN as a sintering aid increases the particle size of LCMO to 1–2 μm for x=0.10. Three orders of magnitude change in electrical resistivity (204 Ω cm for x=0;0.5 Ω cm for x=0.05) is explained on the basis of the difference in the mobility of the charge carriers, by fitting the experimental transport data with a correlated polaron hopping model. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]