The topic of our work is magnetic thin films. Hard magnetic films can be used e. g. for magnetic recording and magnetic microelectromechanical systems. Magnetic Shape Memory films are promising for microactuators and sensors.

In thin films interfaces can be utilized to modify structure, microstructure and hence physical properties. For example the interface towards the substrate allows controlling texture and microstructure during film growth. By this we can prepare films with tailored hard magnetic properties, such as films with improved energy product or very high coercivity. Furthermore, to the free surface of a film can be used to control the magnetic properties. By applying an electrical field through an inert electrolyte we can change the electronic density of states. We use this effect for reversible tuning of coercivity in ultrathin metallic films.

Interfaces are also important for magnetic shape memory (MSM) alloys, a rare class of materials where structure and microstructure can be controlled by a magnetic field. Epitaxial growth can be used for example to freeze unstable states during a martensitic transition. In addition, the martensitic microstructure is constrained by the interface to a rigid substrate. Hence, phase transformation and microstructure in thin films differ compared to bulk. In order to use the large strain up to 10 % in MSM films, they are released from the substrate. At the same time releasing allows us to investigate the influence of the interface by comparing freestanding and constrained films.

Research Topics

• Caloric Films
• Magnetic shape memory films
• Hard magnetic films