Über die ungewöhnlichen optischen und magneto-optischen Eigenschaften von Mangan-dotiertem Zinkoxid

In den letzten Jahren wurde vermehrt versucht durch die Forschung an verdünnten magnetischen Halbleitern (DMS) das Gebiet der Spintronik zu erschließen. In der Spintronik soll nicht nur die Ladung des Elektrons, wie in der herkömmlichen Halbleiterelektronik, genutzt werden, sondern zusätzlich noch d...

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Bibliographic Details
Main Author: Jankowski, Stephanie
Contributors: Heimbrodt, Wolfram (Prof. Dr.) (Thesis advisor)
Format: Doctoral Thesis
Published: Philipps-Universität Marburg 2013
Online Access:PDF Full Text
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In recent years, the field of spintronics has been increasing efforts through research on diluted magnetic semiconductors ( DMS). Spintronics uses the charge of electrons, as in usual semiconductors but also the magnetic moment of the electrons, the so called spin. These materials could be used to develop new methods of sensors and new kind of memories. Thus, it is essential to obtain a deeper knowledge of the electronic and magnetic nature of these materials. ZnMnO is a promising candidate for spintronic applications because of the theoretical predictions of ferromagnetism by room temperature of Dietl et al [1]. Unfortunately it exists neither unanimity about the realizability of ferromagnetism in this material nor exact knowledge about the fundamental electronic and magnetic properties. It becomes apparent that ZnMnO does not follow the chemical trend of the II-Mn-VI-DMS. Within this work ZnMnO crystals have been investigated using optical and magneto-optical methods in order to understand the opto-electronic and opto-magnetic properties. With the gain of this understanding the unusual behavior of this material system can be explained. Therefor a variety of experimental methods have been used, i.e. temperature and polarization dependent photoluminescence measurements within external magnetic fields, absorption measurements, and Raman spectroscopy. The results from these investigations allow a quantitative determination of the excitonic properties and give a consistent view on the internal manganese system. Although the manganese ions occupy Zn sites the d-shell electrons of the manganese do not hybridize with the electrons of the host crystal. The lack of this hybridization is the reason that the magnetic exchange interaction is much smaller as expected. Unfortunately this leads to the conclusion that this material system is not feasible for spintronics. [1] T. Dietl et al. Science 287, 1019 (2000), PRB 63, 195205 (2001)