A04  Spin+Phonons: Exploring the interplay between spins and phonons in micro- and nanostructures of spin crossover materials

Prof. Dr. Volker Schünemann (Department of Physics, TU Kaiserslautern)

Project A04 aims for a deeper physical understanding of phonon mediated first-order phase transitions. Within this project the temperature induced spin state change of iron(II) spin crossover (SCO) compounds will be investigated by means of surface sensitive Mössbauer spectroscopy as well as with synchrotron based nuclear forward scattering (NFS). A special focus will be on the investigation of the spin dependent density of phonon states of SCO nanostructures in comparison to those of 1-D, 2-D and 3-D iron(II) polymers and single molecular crystals. In this way it will be possible to clarify whether hysteresis effects are size dependent on the nanoscale and whether they differ in zero-dimensional (dots), one dimensional (tubes) or two dimensional nanostructures (thin films). A special focus lies on materials which exhibit SCO at room temperature and in which the spin state change is addressable via light. In this way also the spin switching process itself will be investigated by means of ultrafast fs-pump-probe photoelectron spectroscopy techniques in order to explore spin dependent spatiotemporal dynamics.

Aim 1: Understand the interplay between spins and phonons of spin crossover materials from the solid state down to the nanometer scale;

Aim 2: Clarification of the spin dependent spatiotemporal dynamics in nanostructures and thin films of SCO materials after light excitation.

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