Magnetoresistance electronic conductivity

In this chapter the focus is upon electronic conductivity in perovskites. The electrons in perovskites are believed to be strongly correlated that is, they do not behave as a classical electron gas, but are the subject to electron-electron interactions. This leads to considerable modification of the collective electron behaviour of the conduction electrons, resulting in metal-insulator transitions, high-temperature superconductivity, half-metals and colossal magnetoresistance (CMR). The effects of strong correlation are important for the 3d, 4d and4f elements. In many ways the topics described here are thus a continuation of the previous chapter on magnetic perovskites, and in truth the two subject areas cannot be separated in a hard and fast maimer. 

Investigations of the normal state magnetoresistance (MR) as well as the Hall effect and the thermal conductivity in the normal and superconducting mixed states give an important information about the electronic structure and the properties of vortex lattice of the investigated materials. 

Abbreviations AOD, Acousto-optical deflection BCB, bisbenzyocyclobutadiene CCD, indirect contact conductivity detection CL, chemiluminescence ECD, electron capture detector FCS, fluorescence correlation spectroscopy FRET, fluorescence resonance energy transfer ICCD, integrated contact conductivity detection GMR, giant magnetoresistive LED-CFD, light emitting diode confocal fluorescence detector LIF, laser-induced fluorescence LOD, limit of detection MALDI, matrix-assisted laser desorption ionization PDMS, poly(dimethylsiloxane) PMMA, poly(methylmetha-crylate) SPR, surface plasmon resonance SVD, sinusoidal voltammetric detection TLS, thermal lens spectroscopy. 

If the quantum corrections to conductivity are actual the magnetoresistance related to the influence of the magnetic field on these corrections takes place [57-59]. The interference of electrons passing the closed part of trajectory in clockwise and counter-clockwise directions causes the so-called corrections to the conductivity. The phases of the electron wave functions in this case are equal and so this interference is constructive. Therefore, the probability for electrons to come back to the initial point doubles. This leads to the interference corrections which increase the classical resistance. The external magnetic field breaks the left-right symmetry, and the phases collected by the electron wave function while it passes trajectory in clockwise and... 

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