The nanomagnetism group is led jointly by Dr. Andreas Berger (firstname.lastname@example.org) and Dr. Paolo Vavassori (email@example.com). The present research programme for the nanomagnetism group has been divided into three main themes of research:
Theme 1: Magnetization reversal, dynamics, and related characterization methods
- Partially correlated magnetization reversal
Development of theoretical and computational models for achieving a quantitative nano-scale understanding of magnetization reversal in systems with competing interactions (e.g., short-range ferromagnetic exchange and long-range dipolar interactions), such as magnetic recording media with perpendicular anisotropy.
- ΔH-method refinement for general recording media application
Improvement of the reliability and the application range of the ΔH(M,ΔM)-method, which already is the state-of-the-art macroscopic characterization method for magnetic recording media, by including laterally varying inter-granular exchange coupling as well as thermally activated processes. This crucial extension beyond its present limitations has the potential to make the ΔH-method a standard characterization tool in recording media development and manufacturing.
- Single shot dynamics of magnetization reversal events
Experimental study of the magnetization dynamics in high-anisotropy materials induced by ultra-short high-field pulses. This will for the first time allow a direct assessment of the processes and limits for writing and reading information by means of nano-scale magnetic devices and may enable new pathways of how to overcome present limitations. Experimental work will be accompanied by the development of theoretical models to gain a well-rounded physical understanding.
- Fast magnetization dynamics near magnetic ordering temperatures
Extension of experimental work on high-field sub-ns magnetization dynamics into the range of critical points such as the Curie temperature (TC) in ferromagnets. This is a completely unexplored physical regime upon which thermally assisted recording relies, i.e. one of the potential future information technologies.
Theme 2: Fabrication and magnetic properties of multilayered magnetic materials
- Ultra-small grain materials
Development and exploration of strategies for reducing the grain size in functional materials. Technology road-maps for various information technologies envision functional materials with ultra-small grain sizes, far below 10 nm diameter. Reliable and up-scalable fabrication technologies and related scientific issues need to be explored. Here, the potential of the widely used sputter technology will be pursued.
- Meta-magnetic films and meta-magnet based superstructures
Meta-magnetic films will be fabricated and their magnetic and related other physical properties will be studied. Subsequently, growth and magnetic compatibility with adjacent ferromagnetic films will be explored, i.e. the feasibility of meta-magnet based superstructures. Experiments will be complemented by model development and calculations of the magnetic and thermodynamic properties of such systems.
- All-ferromagnetic exchange bias systems with perpendicular anisotropy
Investigations of exchange bias effects using all-ferromagnetic layered systems have elucidated many aspects of the underlying physical mechanisms, including the training effect, as these material systems offer a novel pathway of tuning exchange bias and measuring related magnetic properties. Our past studies will be extended to materials with perpendicular magnetization orientation, for which a rich variety of novel phenomena is to be expected due to the interplay between dipolar interactions and the exchange bias effect.
Theme 3: Fabrication and characterization of magnetic nano-structures
- Magneto-optic diffraction and scattering
Studies of the nano-scale correlation in magnetic patterned structures by designing, building and utilizing novel magneto-optic characterization techniques that exploit the interference and depolarization effects of light being diffracted or scattered by nano-structures.
- Domain-wall structures and dynamics
Manipulation and control of domain wall (DW) structures via geometrical constraints on the nanometer scale and investigation of the underlying mechanisms determining domain wall formation and dynamics: edge roughness, artificial pinning sites, and thermal excitation. Utilization of magnetic DWs and their high-speed displacement for the purpose of ultrafast intense field pulse generation to study the ultrafast mangetization dynamics of nano-magnets. Exploitation of the high controllability of the motion of geometrically constrained DWs for the manipulation of individual nanoparticles in solution on a chip for applications in biotechnology, nanochemistry, and nanomedicine.
- Spintronics effects and devices
Investigation of novel physical processes due to the interplay between spin currents and magnetization dynamics at the nano-scale, such as: spin accumulation, spin torque transfer, and spin waves generation.