Defects structure characterization of NiMnGa alloys by PALS

16th International Conference on Positron Annihilation

Merida, David^1 ; Garcia, Jose Angel^1 ; Plazaola, Fernando^2 ; Sanchez-Alarcos, Vicente^3 ; Pérez-Landazábal, Jose Ignacio^3 ; Recarte, Vicente^3

Fisika Aplikatua II Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao, Spain^1

Elektrizitate Eta Elektronika Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao, Spain^2

Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona, Spain^3

关键词: Annealing temperatures;    Composition ranges;    Ferromagnetic shape memory alloy;    Isochronal annealing;    Maximum temperature;    Positron lifetime;    Positron lifetime spectroscopy;    Positron trapping;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/443/1/012039/pdf
DOI  :  10.1088/1742-6596/443/1/012039

来源: IOP

【 摘 要 】

We have studied the behaviour of defects in off-stoichiometric Ni-Mn-Ga ferromagnetic shape memory alloys by means of positron lifetime spectroscopy. The measurements presented in this work have been performed in six ternary alloys. The studied samples cover a large composition range. Positron experiments have been performed at room temperature after subsequent isochronal annealing at different temperatures up to a maximum temperature of 700°C. Results show a large variation of the average positron lifetime value with the isochronal annealing temperature in three of these samples, with significant differences between them. In the other three, the response is quite different. The results are discussed in terms of different types of positron trapping defects and their evolution with the annealing temperature. The present work shows a high dependence of recovery behaviour with composition in NiMnGa ferromagnetic shape memory alloys.