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Structural transformations in highly oriented seven modulated martensite Ni-Mn-Ga thin films on an Al2O3 (11(2)over-bar0) substrate

Sharma, Amit and Mohan, Sangeneni and Suwas, Satyam (2016) Structural transformations in highly oriented seven modulated martensite Ni-Mn-Ga thin films on an Al2O3 (11(2)over-bar0) substrate. In: JOURNAL OF MATERIALS RESEARCH, 31 (19). pp. 3016-3026.

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Official URL: http://dx.doi.org/10.1557/jmr.2016.317

Abstract

Highly oriented Ni-Mn-Ga thin film with multiple variants and room temperature orthorhombic martensite structure were prepared on a single crystalline Al2O3 (11 (2) over bar0) substrate by DC magnetron sputtering. X-ray diffraction and rocking curve measurements reveal the film as (202)(7M) oriented with an excellent crystal quality ( = 1.8 degrees). Spot-like pole figures indicate that the Ni-Mn-Ga film grows with a strong in-plane preferred orientation. An in-depth analysis of the measured pole figure reveals the presence of a retained austenite phase in the film. Two phase transformations, M-S approximate to 345 K and T-C approximate to 385 K, are observed and are attributed to first order structural transformation from cubic to orthorhombic, and second order phase transformation from ferromagnetic to paramagnetic, respectively. In situ high temperature x-ray diffraction measurements provide a clear indication of a thermally-induced martensite austenite reversible structural phase transformation in the film. The presence of martensite plates with seven modulated orthorhombic structure and adaptive nano-twins are some of the important microscopic features observed in the film with transmission electron microscopy investigations.

Item Type: Journal Article
Additional Information: Copy right for this article belongs to the CAMBRIDGE UNIV PRESS, 32 AVENUE OF THE AMERICAS, NEW YORK, NY 10013-2473 USA
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Division of Interdisciplinary Research > Centre for Nano Science and Engineering
Depositing User: Id for Latest eprints
Date Deposited: 07 Dec 2016 05:10
Last Modified: 07 Dec 2016 05:10
URI: http://eprints.iisc.ac.in/id/eprint/55483

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