Multiband models for colossal magnetoresistance materials and diluted magnetic semiconductors
by Popescu, Florentin, Ph.D., THE FLORIDA STATE UNIVERSITY, 2007, 133 pages; 3282657

Abstract:

Several multiband models for Colossal Manetoresistance Materials and Diluted Magnetic Semiconductors are investigated within Dynamical Mean-Field Theory. The theoretical analysis of such models uses extensively the parametrization method for the bare Green's function to study the critical transition temperatures in a wide range of model's parameters; hoping amplitudes, couplings, and carrier concentrations. For both classes of materials, it is found within a two-band model that the transition temperature can be twice larger than the one predicted by the one band models and that its maximum is reached at a twice larger carrier concentration. It is also revealed that the off-diagonal hoppings, when considered, lead to a substantial boost of the ferromagnetic transition temperature. By accounting for the attractive Coulomb potential by acceptors in diluted magnetic semiconductors, the impurity to valence band crossover is studied as a function of doping and the critical values of doping, at which the crossover occurs, are estimated for various diluted magnetic semiconductors.

 
Advisor
SchoolTHE FLORIDA STATE UNIVERSITY
SourceDAI/B 68-09, p. , Dec 2007
Source TypeDissertation
SubjectsCondensed matter physics
Publication Number3282657
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