Neutron spectroscopy study of magnons in the austenite and martensite phases of a Ni-Mn-Ga Heusler alloy

Runov, V.; Stuhr, U.

doi:10.1016/j.jmmm.2010.09.013

Neutron spectroscopy study of magnons in the austenite and martensite phases of a Ni-Mn-Ga Heusler alloy

Runov V & Stuhr U

Citation

Runov, V., & Stuhr, U. (2011). Neutron spectroscopy study of magnons in the austenite and martensite phases of a Ni-Mn-Ga Heusler alloy. Journal of Magnetism and Magnetic Materials, 323(2), 244-247. https://doi.org/10.1016/j.jmmm.2010.09.013

Persistent URL https://www.dora.lib4ri.ch/psi/islandora/object/psi:13991

The low energy region of magnon excitations of an off-stoichiometric Ni_49.1MN_29.4Ga_21.5 single crystal has been investigated by neutron spectroscopy. The lowest magnetic exchange stiffness constant D of 97±2 meV Å² has been found in the cubic austenite phase. In the two martensitic phases the exchange stiffness constants are significantly larger with values of 149±4 meV Å² in the tetragonal phase and 198±7 meV Å² in the low temperature martensite. The large value of D in the low temperature phase compared to the other phases cannot be explained solely by renormalization effects due to magnonmagnon interaction and is attributed to a stronger magnetic coupling. In both the martensitic phases a gap of magnon excitation at the Γ-point of about 0.2 meV was observed.