Martin Luther University Halle-Wittenberg

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B1: Defect-induced magnetism in oxides

The aim of the project is the experimental and theoretical investigation of defect-induced magnetic order in diamagnetic oxides generated by the incorporation of defects such as vacancies and / or doping with nonmagnetic elements that leads to the appearance of magnetic ordering at high temperatures. It is expected that the defect-induced magnetism (DIM) will find long-term applications in spintronics or opto-spintronics.

During the last funding period, new experimental methods had been developed, which allow a reproducible production of defect-induced magnetism in micro- and nanostructures. Through intensive collaboration between theory and experiment the understanding of this phenomena could be deepened. Defect-induced magnetism leads to magnetic field dependence of physical processes such as, for example, in the photoconductivity. The intensive study of these effects is necessary to get a better understanding of DIM, but also to pave the way for new measuring principles and applications. Because of the produced DIM in the studied oxides is mostly determined by surface properties or near-surface areas, a local study of the magnetic structure on the surface is indispensable. This will be possible through the construction and implementation of a new magnetometer. Three oxide systems will be further investigated: ZnO:Li:H (magneto-photoconductivity, thermoelectric effect), TiO2 (proof of applicability of the experimental techniques to generate and detect DIM), zinc ferrite (manipulation of magnetic properties by defect engineering). The theoretical studies will be focused on the description of the microscopic origin of the defect-induced magnetism in the experimentally studied systems, in which the emergence of collective magnetism, through the sample treatment produced individual defects, will be a focal point. In particular, the work on defects and inversion of zinc ferrite will be continued. In connection with the development of the new magnetometer also defects on surfaces will be investigated. The results of the measurements on photoactive magnetic oxides should be interpreted on the basis of microscopic defect models.

Principal Investigators

Prof. Dr. Pablo D. Esquinazi ⇒

phone: +49 (0) 341/97 32751

fax: +49 (0) 341/97 32668

Prof. Dr. Pablo D. Esquinazi

Prof. Dr. Pablo D. Esquinazi

Prof. Dr. Wolfram Hergert ⇒

phone: +49 (0) 345/5  525445

fax: +49 (0) 345/55 25446