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Title: Vacancy dynamic in Ni-Mn-Ga ferromagnetic shape memory alloys

Vacancies control any atomic ordering process and consequently most of the order-dependent properties of the martensitic transformation in ferromagnetic shape memory alloys. Positron annihilation spectroscopy demonstrates to be a powerful technique to study vacancies in NiMnGa alloys quenched from different temperatures and subjected to post-quench isothermal annealing treatments. Considering an effective vacancy type the temperature dependence of the vacancy concentration has been evaluated. Samples quenched from 1173 K show a vacancy concentration of 1100 ± 200 ppm. The vacancy migration and formation energies have been estimated to be 0.55 ± 0.05 eV and 0.90 ± 0.07 eV, respectively.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ; ; ;  [4] ;  [5]
  1. Fisika Aplikatua II Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain)
  2. (Spain)
  3. (Basque Centre for Materials, Application and Nanostructures), 48040 Leioa (Spain)
  4. Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain)
  5. Elektrizitate eta Elektronika Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain)
Publication Date:
OSTI Identifier:
22300273
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 104; Journal Issue: 23; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; ANNIHILATION; FORMATION HEAT; GALLIUM ALLOYS; MANGANESE ALLOYS; MIGRATION; NICKEL ALLOYS; PHASE TRANSFORMATIONS; POSITRONS; SHAPE MEMORY EFFECT; SPECTROSCOPY; TEMPERATURE DEPENDENCE; VACANCIES