Controlled creation of defect-induced magnetism (DIM) in graphite- and diamond-based films

• Applicants: Professor Dr. Pablo David Esquinazi; Professor Dr. Jan Meijer
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 330696097

Defect Induced Magnetism (DIM) is a new phenomenon in solid state physics that makes possible to create magnetic order above room temperature in certain atomic lattice structures of nonmagnetic, semiconducting or insulating materials by introducing lattice defects with a density of the order of 5%. The aim of this proposal is to create DIM via irradiation in graphite and diamond thin films, within a very small lateral scale and well-defined conditions. The creation of defects will be performed using collimated and focused ion beams, including unique nano-implanter and a single ion irradiation systems. We pursue to answer several open questions regarding this phenomenon that are necessary to clarify in order to understand the phenomenon itself and to increase the efficiency to produce materials with DIM, namely: How does this magnetic order develop as a function of the defect density? How large is the minimum defect density necessary to create magnetic order below a certain temperature? Can one systematically tune the Curie temperature as a function of defect density? How stable are the defects that contribute to DIM and how the magnetic order weakens after reaching a certain threshold density? How can the generation of the defects be improved? For the measurement of the magnetic stray fields produced by single and an ensemble of defects on graphite and diamond samples we will use a method with high space and field resolution, similar to the one based on the optical detection of nuclear magnetic resonance of nitrogen-carbon vacancies in diamond. The field sensitivity of this method will be radically improved through a new hardware and software approach.

• DFG Programme: Research Grants
• Major Instrumentation: Arbiträrgenerator ; Helium-Vektormagnet Kryostat mit VTI ; Mikrowellen-Generator
• Instrumentation Group: 0120 Supraleitende Labormagnete ; 6040 Frequenz-Umformer (statisch) und Hochfrequenzgeneratoren ; 6300 Meßgeneratoren, Meßsender, Frequenznormale