Crystal structure, magnetic anisotropy, and mechanical properties of seven-layered martensite in Ni-Mn-Ga

Alexei Sozinov; Alexander Anatolyevich Likhachev; Nataliya Lanska; Kari Ullakko; Veikko K. Lindroos

doi:10.1117/12.474976

11 July 2002 Crystal structure, magnetic anisotropy, and mechanical properties of seven-layered martensite in Ni-Mn-Ga

Alexei Sozinov, Alexander Anatolyevich Likhachev, Nataliya Lanska, Kari Ullakko, Veikko K. Lindroos

Proceedings Volume 4699, Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics; (2002) https://doi.org/10.1117/12.474976
Event: SPIE's 9th Annual International Symposium on Smart Structures and Materials, 2002, San Diego, California, United States

Abstract

Magnetic-field-induced strain of about 10 percent is reported in Ni_48.8Mn_29.7Ga_21.5 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.

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Alexei Sozinov, Alexander Anatolyevich Likhachev, Nataliya Lanska, Kari Ullakko, and Veikko K. Lindroos "Crystal structure, magnetic anisotropy, and mechanical properties of seven-layered martensite in Ni-Mn-Ga", Proc. SPIE 4699, Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics, (11 July 2002); https://doi.org/10.1117/12.474976

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