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Proceedings Paper

Crystal structure, magnetic anisotropy, and mechanical properties of seven-layered martensite in Ni-Mn-Ga
Author(s): Alexei Sozinov; Alexander Anatolyevich Likhachev; Nataliya Lanska; Kari Ullakko; Veikko K. Lindroos
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Paper Abstract

Magnetic-field-induced strain of about 10 percent is reported in Ni48.8Mn29.7Ga21.5 alloy at ambient temperature in a magnetic field order of 1 T. It was confirmed by different experimental methods that the strain is contributed by twin boundary motion. The crystal structure of thermally-induced martensitic phase in this alloy was found to be close to orthorhombic one in temperature range from 245 K to 333 K with lattice parameters a equals 0.619 nm, b equals 0.580 nm, c equals 0.553 nm (relating to the cubic parent phase coordinates) at ambient temperature. More detailed x-ray studies revealed seven-layer shuffling-type modulation along and directions. High magnetic anisotropy properties were found for this phase. The magnetic measurements revealed that the shortest axis (c-axis) is the axis of easiest magnetization, the longest (a-axis) is the axis of hard magnetization, and b-axis is the intermediate one. The orthorhombic phase has low twinning stresses. The compressive stress applied along a-axis of single-variant sample at most 2 MPa is enough to produce approximately 10 percent strain realized by twin boundary motion. The necessary conditions for observation a giant magnetic-field-induced strain in non-stoichiometric Ni2MnGa alloys based on the new experimental data are discussed.

Paper Details

Date Published: 11 July 2002
PDF: 11 pages
Proc. SPIE 4699, Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics, (11 July 2002); doi: 10.1117/12.474976
Show Author Affiliations
Alexei Sozinov, Helsinki Univ. of Technology (Finland)
Alexander Anatolyevich Likhachev, Helsinki Univ. of Technology (Finland)
Nataliya Lanska, Helsinki Univ. of Technology (Finland)
Kari Ullakko, Helsinki Univ. of Technology (Finland)
Veikko K. Lindroos, Helsinki Univ. of Technology (Finland)

Published in SPIE Proceedings Vol. 4699:
Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics
Christopher S. Lynch, Editor(s)

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