J. Phys. IV France 112 (2003) 963
DOI: 10.1051/jp4:20031041

Temperature dependence of martensite structure and its effect on magnetic-field-induced strain in Ni ₂MnGa magnetic shape memory alloys

N. Glavatska¹, G. Mogilniy¹, I. Glavatsky¹, S. Danilkin², D. Hohlwein², A. Beskrovnij^{3, 4} and V.K. Lindroos<sup>4

1</sup>  Institute for Metal Physics, Vernadsky Blvd. 36, 03680 Kiev 142, Ukraine
²  Hahn-Meitner-Institut, Glienicker Str. 100, 14109 Berlin, Germany
³  Joint Institute for Nuclear Research, Joliot-Curie Str. 6, Dubna, Moscow Region 141980, Russia
⁴  Helsinki University of Technology, P. O. Box 6200, 02015 Hut, Finland

Abstract
Structure in two Ni ₂MnGa alloys, that exhibit large magnetic field induced strain in martensite phase, was studied with neutron diffraction in temperature range 4K-354K. It is found that lattice parameters in martensite notably change with temperature. The magnetic field induced strain value decreases/rises with the rise/decrease of temperature according to the change of (l-c/a) in martensite phase. The critical value of the magnetic field for activation of the twin's boundary motion decreases with increasing temperature.

© EDP Sciences 2003