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Comparing properties of substrate-constrained and freestanding epitaxial Ni–Mn–Ga films / Anja Backen in Acta materialia, Vol. 58 N° 9 (Mai 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 9 (Mai 2010) . - pp. 3415–3421 Titre : Comparing properties of substrate-constrained and freestanding epitaxial Ni–Mn–Ga films Type de document : texte imprimé Auteurs : Anja Backen, Auteur ; Srinivasa R. Yeduru, Auteur ; Manfred Kohl, Auteur Année de publication : 2011 Article en page(s) : pp. 3415–3421 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Magnetic  shape  memory  alloy  Epitaxial  Thin  films  Interfaces  Ni–Mn–Ga Résumé : In order to use the magnetic shape memory alloy Ni–Mn–Ga with its high achievable strain of up to 10% for microactuators, freestanding epitaxial films are required. Here we show that these conditions can be fulfilled when using chromium as a sacrificial layer. The low misfit towards Ni–Mn–Ga enables epitaxial growth. Furthermore, Cr can afterwards be removed selectively by wet-chemical etching and during deposition no significant interdiffusion is observed. The structure, microstructure and magnetic properties of micrometer thick films are not affected by the etching process. Films are ferromagnetic at room temperature and we observe the coexistence of non-modulated (NM) and seven layered modulated (14 M) martensite. Tensile stress–strain measurement of a freestanding bridge reveals a broad strain plateau of 12% at a twinning stress of 25 MPa, indicating reorientation of NM variants. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410001023 [article] Comparing properties of substrate-constrained and freestanding epitaxial Ni–Mn–Ga films [texte imprimé] / Anja Backen, Auteur ; Srinivasa R. Yeduru, Auteur ; Manfred Kohl, Auteur . - 2011 . - pp. 3415–3421. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 9 (Mai 2010) . - pp. 3415–3421 Mots-clés : Magnetic  shape  memory  alloy  Epitaxial  Thin  films  Interfaces  Ni–Mn–Ga Résumé : In order to use the magnetic shape memory alloy Ni–Mn–Ga with its high achievable strain of up to 10% for microactuators, freestanding epitaxial films are required. Here we show that these conditions can be fulfilled when using chromium as a sacrificial layer. The low misfit towards Ni–Mn–Ga enables epitaxial growth. Furthermore, Cr can afterwards be removed selectively by wet-chemical etching and during deposition no significant interdiffusion is observed. The structure, microstructure and magnetic properties of micrometer thick films are not affected by the etching process. Films are ferromagnetic at room temperature and we observe the coexistence of non-modulated (NM) and seven layered modulated (14 M) martensite. Tensile stress–strain measurement of a freestanding bridge reveals a broad strain plateau of 12% at a twinning stress of 25 MPa, indicating reorientation of NM variants. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410001023