Lattice dynamics contribution to the magnetic properties of molecular magnets: Raman and ultrasonic studies

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This proposal concerns high resolution Raman scattering and ultrasonic studies of two classes of molecular magnetic compounds: I) spin-crossover systems, which demonstrate spin state change under influence temperature and/or pressure as well light irradiation; II) single-molecular magnets consisting of polynuclear transition metal ion complexes bound by organic ligands. The main goal of this project is the investigation of the role of intermolecular vibrations for the cooperative behavior of spin crossover transitions for case I systems. Spin phonon interactions and the determination of phonon modes which strongly affect the efficiency of magnetic exchange paths will be main aim for case II systems. Raman scattering and ultrasonic studies will be performed in wide temperature range (2 K - 300 K), magnetic fields up to 7 T and under hydrostatic pressure up to 2GPa. The role and influence of lattice degrees of freedom on the spin state crossover mechanisms in the case I and in quantum tunneling mechanism of magnetization in the case II will be elucidated. The second goal of the project is the search of the spin state gap as well as its temperature evolution for case I systems and the manifestation of inelastic many spin effects in Raman spectra in case II systems. Lattice dynamical calculations will be executed through access to codes: WIEN2k, Gamess and others. The stability of different spin states against different type of lattice distortions will be analyzed with help of modified crystal approach with inclusion of spin-orbital interaction. The crystals to be investigated are tetranuclear and hexanuclear Fe, Mn12 and spin crossover systems available due to collaborations within the DFG Priority Programme 1137