University of Bielefeld

University of Bielefeld

The University of Bielefeld (UNIBI) was designed and has evolved as a strong research university with a focused spectrum of cross-disciplinary research fields in the natural sciences and technology. Major research areas in the Thin Films and Physics of Nanostructures Group are Ultrathin films, Nano-magnetism, Spintronics and Biophysics. The main goals of our work are the basic understanding of magnetism and spin-dependent electronic transport in thin films and nanostructures, the development of optimized magneto- and spin-electronic devices and new applications of magnetic devices in sensors, information and biotechnology.

The group of Prof. Reiss has worked for many years on spin electronics. In particular, magnetic tunnel junctions turned out to be a key device for studying both fundamental properties such as spin dependent transport as well as new applications such as STT-MRAM. The group has very successfully worked on these fields and was one of the first to report a large tunnelling magnetoresistance using Heusler alloys. Additionally, dynamic properties have been studied on the device level. Recently, also spin caloric properties have been studied in collaboration with researchers in Göttingen and Braunschweig and neuronomorphic networks with tunnel junctions have been demonstrated.

The group of Prof. Reiss has at present about 40 members and is one of the largest groups working on spinelectronics and its applications in Europe. Within the last years, the capabilities in thin film deposition, characterization and patterning as well as in prototyping devices have been improved considerably. The group owns various deposition tools and will use its largest system (16 sources UHV-cosputtering) for this project. In this system, many Heusler alloys have already been successfully deposited and at present, research on magnetically perpendicular materials is going on. For characterizing the films, X-ray diffraction (Philips with Euler cradle), AGM and systems for measuring transport-, tunnelling- and Hall-Effect in a temperature range from 300mK to 500K are available.

UNIBI will carry out the optimisation of epitaxial Heusler alloy film growth using combinatorial sputtering and molecular-beam epitaxy (MBE) systems with the focus on perpendicular anisotropy. The scalability of the material- and exchange-bias properties is also evaluated by UNIBI. Demonstrator devices will be produced at the end of the project: initially simple tri-layer spin valve structures will be evaluated but, once materials with real potential to produce the desired functionality are obtained, more complex structures such as magnetic tunnel junctions (MTJs) will be used.

UNIBI has large experience in its main task in the project, i.e. in the preparation of spin electronic devices including exchange biasing and new materials such as Heusler alloys. It will contribute using the know-how on Heusler materials (Selection of alloys) and will do X-ray diffraction to evaluate the structural properties of the Heusler films – studies of the magnetic properties will also be contributed. UNIBI will lead the work on device concepts and evaluation by its core expertise in e-beam lithography of magnetic film systems such as magnetic tunnel junctions including Heusler alloys.