A model study for Eu-rich EuO [Elektronische Ressource] / von Peter Sinjukow

A model study for Eu-rich EuOD I S S E R T A T I O Nzur Erlangung des akademischen Gradesdoctor rerum naturalium(Dr. rer. nat.)im Fach Physikeingereicht an derMathematisch-Naturwissenschaftlichen Fakult at IHumboldt-Universit at zu BerlinvonHerrn Dipl.-Phys. Peter Sinjukowgeboren am 04.08.1974 in Karl-Marx-StadtPr asident der Humboldt-Universit at zu Berlin:Prof. Dr. Jurgen MlynekDekan der Mathematisch-Naturwissenschaftlichen Fakult at I:Prof. Thomas Buckhout, PhDGutachter:1. Prof. Dr. Wolfgang Nolting2. Prof. Dr. Robert Keiper3. Prof. Dr. Wladyslaw Borgieleingereicht am: 20. August 2004Tag der mundlic hen Prufung: 7. Dezember 2004AbstractIn this thesis a model is formulated for Eu-rich EuO. It consists in an ex-tension of the Kondo lattice model (KLM). For the KLM only a few exactstatements exist. To those we add a new one, namely the exact mappingof the periodic Anderson model on the antiferromagnetic KLM for arbitrarycoupling constant J.Pure EuO is a ferromagnetic semiconductor. Eu-rich EuO exhibits ahuge metal{insulator transition near the Curie temperature with a jump inresistivity of up to 13 orders of magnitude. It is the biggest jump in resistivityever observed in nature. We theoretically reproduce this jump with the Kuboformula. We achieve very good ts already within a not fully self-consistenttheory where the magnetization of the Eu spins is taken from a Brillouinfunction.