Browsing by Author "Fufa, Dereje"

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    Study of Effects of Magnon-Exciton Interaction on Ferromagnetism of Diluted Magnetic Semiconductors
    (Addis Ababa University, 2017-06) Fufa, Dereje; Amente, Chernet (PhD)
    In this thesis the e ect of exciton-magnon interaction on Diluted Magnetic Semiconduc- tors (DMS) is theoretically studied employing quantum eld theory. The double time temperature Green function technique is used to nd dispersion whereby single mode magnon number is obtained from spectral density calculations. It is understood that the existence of exciton and magnon coupling increases total number of magnons which is the reason for decrease in magnetization leading to lowering of ferromagnetic transition temperature Tc. This is perhaps due to scattering of orientations of introduced magnetic spins. The disorder is attributed as enhanced by long time coupling of electron-hole pair, reducing number of holes that mediate ferromagnetism. At lower temperatures the impu- rity concentration, x and Tc direct relation is known to violate due to the T1=2 containing factor dominance