Helium bath cryostat with magnetic field and microwave system for confocal optically detected magnetic resonance and transport studies ('spintronic platform')

• Subject Area: Condensed Matter Physics
• Term: Funded in 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 431696304

A 'spintronic measurment platform' is requested that allows to study samples at variable temperatures and magnetic fields with simultaneous microwave irradiation. Two types of measurement are targeted: confocal-optic microscopy such as optically detected magnetic resonance on individual NV color centers in diamond, and electronic transport with free choice of the relative orientation between sample and magnetic field. A comparable setup is lacking at the Universität Osnabrück.1. NV color centres in diamond are used as quantum sensors for electron spin systems in their environment. Such systems may be endohedral fullerenes, which are prepared on site for use as quantum bits in information processing, or spin-labelled molecules that serve for structure elucidation in biological environments. Further spin-carrying molecular or inorganic systems – e.g., rare-earth doped nano-particles – can also be studied with this method. The platform needs a high mechanical stability for such studies, as well as a 3D-piezo scanner.2. Transport measurements are essential for the study of field-effect transistors based on carbon nanotubes. Chemical modifications of the nanotube (e.g., by grafting or encapsulating other molecules) as well as a functionalization of the electrical contacts (e.g., by integrating tunnel barriers and/or spin filters) allow to use the transistors as novel detectors (for internal molecular states in the former case, as magnetoresistive elements with switchable sensitivity in the latter case). Good control of the orientation between nanotubes and/or contacts relative to the magnetic field is of utmost importance.3. Magnetotransport in magnetic oxide layers with or without magnetic molecular adlayers will complement the available comprehensive set of analysis techniques (X-Ray based or magnetometry) for these classes of materials. This will enable specific studies to tune the magnetoelectronic structure of ultrathin films for spintronics.4. Magnetotransport in organic semiconducting devices (z.B. spin valves, organic magnetoresistors) depends on spin states of largely varying energy (from proton nuclear states to strongly coupled electron spins). Such states can be best studied by spin resonance. The platform will enable us to implement electrically detected magnetic reonance over large spans of magnetic fields and microwave energies via tailored micro-resonators to gain fundamentally new insights in this research area. Of particular interest is the possibility to vary either the sample/field geometry or the optical excitation of the devices with highest precision.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Helium-Badkryostat mit Magnetfeld und Mikrowellensystem für konfokal-optisch detektierte Magnetresonanz und Transportmessungen ("Spintronische Messplattform")
• Instrumentation Group: 0120 Supraleitende Labormagnete
• Applicant Institution: Universität Osnabrück
• Leader: Professor Dr. Wolfgang Harneit