Berlin 2012 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 53: Joint Session Magnetic Shape Memory Alloys II (jointly with DS, MA)
MM 53.9: Talk
Thursday, March 29, 2012, 17:15–17:30, H 0112
Vibrational properties of Ni-Mn-Ga ferromagnetic shape memory alloys in the austenite phase — •Semih Ener1, Jürgen Neuhaus1,2, and Winfried Petry1,2 — 1Technische Universität München, Lehrstuhl für Funktionelle Materialien, Garching, Germany — 2Technische Universität München, Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Garching, Germany
In the ferromagnetic shape memory Ni-Mn-Ga alloys the structural transition can be driven either by an external magnetic field or temperature. In this work we investigate the effect of temperature on the vibrational properties of Ni2MnGa and Ni49Mn32Ga19 in the austenite phase by using mainly inelastic neutron scattering. The measurements were done at the Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Garching. The Born-von Kármán model is applied to the Ni2MnGa full phonon dispersion in the austenite phase and macroscopic properties are calculated from this model. The effect of temperature on the phonon softening in TA2[110] phonon branch is investigated in detail in a wide temperature range for both Ni2MnGa and Ni49Mn32Ga19. The relations between the phonon softening and the structural transition are well understood for both compositions but the effect of magnetic ordering is not comprehended especially for the off-stoichiometric composition.