POLARON AND SPIN-POLARON EFFECTS IN THE COLOSSAL MAGNETORESISTANCE

The polaron formation due to the strong interaction of electrons with the optical phonons in a layered manganese oxides is considered. The diffusion of nearly localized polarons in the presence of the spin-dependent and multiple scattering on the randomly oriented and/or distributed magnetic moments of atoms is considered. The spin diffusion coefficient in the case of the exchange interaction between the diffusive but nearly localized polarons is evaluated. It is shown that the polaron localization leads to the vanishing of the spin diffusion and hence the ferromagnetic phase transition. The spin-polaron effect caused by the interaction of polarons with the spin fluctuations further significantly reduces conductivity near the temperature of the ferromagnetic phase transition as shown.

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Conductivity and Isotope Effect in the Colossal Magnetoresistance

International Journal of Modern Physics B ◽

10.1142/s0217979298002738 ◽

1998 ◽

Vol 12 (29n31) ◽

pp. 3397-3405 ◽

Cited By ~ 1

Author(s):

Y. M. Malozovsky ◽

J. D. Fan ◽

D. Bagayoko

Keyword(s):

Curie Temperature ◽

Isotope Effect ◽

Colossal Magnetoresistance ◽

Manganese Oxides ◽

Spin Diffusion ◽

Magnetic Moments ◽

Ferromagnetic Phase ◽

Temperature Dependence Of Conductivity ◽

Ferromagnetic Phase Transition ◽

Localized Electrons

The diffusion of nearly localized electrons is considered in the presence of the spin-dependent and multiple scattering on the randomly oriented and/or distributed magnetic moments of scatterers. The spin diffusion coefficient in the case of the exchange interaction between the diffusive but nearly localized electrons is evaluated. It is shown that the electron localization leads to the vanishing of the spin diffusion and hence the ferromagnetic phase transition. The isotope effect in the Curie temperature in the case of the electron–phonon inelastic relaxation is obtained, as experimentally observed in the manganese oxides by Zhao and co-workers.11 The strong spin-polaron effect caused by the interaction of the diffusive electrons with the diffusive paramagnons significantly reduces conductivity near the Curie temperature. The temperature dependence of conductivity in the absence and presence of an external magnetic field is discussed as well.

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Effect of High-Energy Electron Irradiation on the Transport and Magnetoresistive Behavior in La0.64Ca0.36MnO3 Films

International Journal of Modern Physics B ◽

10.1142/s0217979298002751 ◽

1998 ◽

Vol 12 (29n31) ◽

pp. 3409-3411 ◽

Cited By ~ 1

Author(s):

A. Parasiris ◽

K. D. D. Rathnayaka ◽

D. G. Naugle ◽

B. I. Belevtsev ◽

V. B. Krasovitsky ◽

...

Keyword(s):

Phase Transition ◽

Point Defects ◽

Electron Irradiation ◽

Colossal Magnetoresistance ◽

Oxygen Depletion ◽

High Energy ◽

Ferromagnetic Phase ◽

High Energy Electron ◽

In Doping ◽

Ferromagnetic Phase Transition

Defects introduced by irradiating LaCaMnO films with high-energy (≃ 6 MeV ) electrons produce a significant increase in film resistivity but have only a small effect on the colossal magnetoresistance and the temperature of the ferromagnetic phase transition. These results suggest that electron irradiation produces mainly point defects rather than a change in doping by oxygen depletion.

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