Lattice dynamics in ferromagnetic shape memory alloys (Diplomarbeit)

SPITZENFORSCHUNG SICHERT ARBEIT, FÖRDERT ZUKUNFT

Description

Would you be able to deform a piece of metal up to 11% of its length just by pressing it with fingers or applying a magnetic field? Yes ! if this is a magnetic shape memory alloy. These are smart materials able to recover large strain under moderate applied magnetic fields. Ni­based alloys such as Ni2MnGa are typical candidates for such a use. Prerequisite for the occurrence of a shape memory effect is a structural transformation from a high­temperature phase (austenite) to a low­temperature phase (martensite). This transformation is due to low­restoring forces against specific atomic vibrations (phonons) easily identified from their anomalous softening with decreasing temperature.

We propose, in the frame of this Diplomarbeit, the investigation of the lattice dynamics in the austenitic and martensitic phases of different Ni­based shape memory alloys by means of inelastic neutron scattering on single crystals. This work aims to address open questions regarding the interplay of the magnetic properties and the vibration degrees of freedom. The measurements will be performed using the three­axis spectrometers PUMA and PANDA at the Forschungsneutronenquelle Heinz Maier-­Leibnitz in Garching. A part of the experiments will eventually be performed at the Laboratoire Léon Brillouin in Saclay (France). This work is a part of a priority program (SPP1239, http://www.magneticshape.de) of the Deutsche Forschungsgemeinschaft change of the microstructure and form of solid materials by external magnetic fields. The work is topic to a close collaboration with the group of Dr. Schneider (HMI, Berlin) for the sample preparation together with Prof. Entel's and Prof. Acet's groups from Duisburg University for the first­principle calculations and the magnetic properties.

  Prof. Dr. Winfried Petry, Email: winfried.petry@frm2.tum.de Phone: +49 89 289 14704, Fax: +49 89 289 14666
Technische Universität München, Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Lichtenbergstraße 1 D-85747 Garching Germany