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MA: Fachverband Magnetismus

MA 23: Magnetic Shape Memory Alloys I (jointly with MM)

MA 23.3: Talk

Tuesday, March 15, 2011, 12:45–13:00, HSZ 04

Effect of temperature and compositional changes on the vibrational properties of Ni-Mn-Ga alloys — •Semih Ener¹, Jürgen Neuhaus^1,2, Richard Mole², Klaudia Hradil², and Winfried Petry^1,2 — ¹Technische Universität München, Physik Department E13, Garching, Germany — ²Technische Universität München, Forschungsneutronenquelle Heniz Maier-Leibnitz (FRM II), Garching, Germany

In Ni-Mn-Ga ferromagnetic shape memory alloys (FSMAs) the instability of the lattice as observed in the phonon spectra causes the structural transition by changing the temperature or by applying magnetic field in a particular direction. In this work we investigate the vibrational properties of two different FMSAs, Ni₂MnGa and Ni₄₉Mn₃₂Ga₁₉. The full phonon dispersions of these materials are compared with theoretical first principle phonon calculations. The inelastic neutron scattering experiments performed at the Forschungsneutronenquelle Heniz Maier-Leibnitz (FRM II) in addition to calorimetric and magnetic measurements give a detailed insight in the anomalous behavior around the structural and magnetic transition temperatures. The vibrational properties of austenite-premartensite (3M) phase and austenite-martensite (5M) phase transitions were investigated in detail to understand the differences between these two transitions. The results show same overall behavior for different compositions but the relation between the magnetic ordering and the phonon remains an open question as their particular behavior appeared at different temperatures.