Fifth European Symposium on Martensitic Transformations and Shape Memory Alloys

J. Phys. IV France 11 (2001) Pr8-311-Pr8-316
DOI: 10.1051/jp4:2001853

Large magnetic-field-induced strains in Ni-Mn-Ga alloys in rotating magnetic field

A. Sozinov¹, Y. Ezer¹, G. Kimmel², P. Yakovenko³, D. Giller⁴, Y. Wolfus⁴, Y. Yeshurun⁴, K. Ullakko⁵ and V.K. Lindroos<sup>1

1</sup>  Helsinki University of Technology, Laboratory of Physical Metallurgy and Materials Science, P.O. Box 6200, 02015 Hut, Finland
²  Ben-Gurion University, Department of Materials Engineering, P.O. Box 653, Beer-Sheva, Israel
³  Institute for Metal Physics, Laboratory of Thermo-Mechanical Treatment, 003680 Kiev 142, Ukraine
⁴  Department of Physics, Bar-IIan University, Ramat Gan 52900, Israel
⁵  Helsinki University of Technology, Laboratory of Biomedical Engineering, P.O. Box 2200, 02015 Hut, Finland

Abstract
A single-crystal samples of near-stoichiometric Ni₂MnGa alloys with large magnetic field induced strain (MSM effect) at room temperature have been investigated. It was found that there is a reversible reorientation of easy magnetization direction and magnetic domain structure under applied magnetic field. By means of x-ray Laue diffraction method and difractometric analysis it was ascertained that these phenomena are connected with the growth of martensitic twin variant with the short crystallographic axis (c-axis) directed along the applied magnetic field. Furthermore, by means magneto-optical investigations we have found the correlation between martensitic microstructure and magnetic domain structure. The field-induced reorientation of martensite was able to change the dimensional lengths of the samples more than 4.5 %.

© EDP Sciences 2001