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B1: Defect-induced magnetism in oxides

The goal of this project is the experimental and theoretical investigation of defect-induced magnetic ordering in nominally diamagnetic oxides. The experimental and theoretical work done in the first period agrees with the general consensus reached that defects, such as vacancies or doping with non-magnetic elements segments, is the main reason for the occurrence of magnetic ordering in diamagnetic oxides. For the next period crystals and thin layers of nominally diamagnetic oxides will continue be studie. In order to produce ferromagnetism, the layers are partially doped with non-magnetic elements, or prepared by using hydrogen plasma treatment. Measurements of surface-sensitive x-ray circular magnetic dichroism (XMCD) will try to clarify the polarization of the 2p bands of oxygen. A main focus will be the measurent of the transport properties of micro-and nano-structures. We also plan to study the influence of light on the magnetic properties of oxide structures. The theoretical investigations are continuing on ab initio level for the interpretation of experimental results. From the ab initio calculations in addition to the exchange parameters, effective pair interactions can be extracted. This will allow to simulate segregation effects of defects at or near the surface. Thus realistic estimates of the transition temperatures are possible. We will examine theoretical models for the photoconductivity of defect-induced magnetic oxides.

Principal Investigators

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