Correspondence:
[*]
Institute of Magnetism, Vernadsky str. 36, Kiev 03142, Ukraine.
Tel.: +380 44 444 95 91; Fax: +380 44 444 10 20; E-mail: chern@imag.kiev.ua
Abstract: The magnetostriction measurements of almost stoichiometric single
crystalline Ni_2MnGa compound with
T_m<T_C (T_m and T_C
are the martensitic and ferromagnetic transformation temperatures respectively)
at constant temperatures have been performed in a temperature range of 100--400
K. The measurements resulted in a temperature evolution of magnetostrain,
\varepsilon, with two extremums caused by soft mode
condensation and martensitic transformation. Magnetic field induced strain of
0.4% In turn, the dilatometric mode of measurements along [100] under magnetic
field (either constant or cyclic) led to 1.5% strain in martensite. Using a
phenomenological approach both the anisotropic and volume magnetoelastic
constants have been evaluated in cubic phase to be equal to
-1.2 MPa and -0.4 GPa respectively. The
experimentally observed smearing of Curie temperature in single crystalline
Ni_{51.2}Mn_{31.1}Ga_{17.7}alloy
with T_m>T_C is quantitatively explained by the spatially
inhomogeneous mass density of martensitic phase and volume
magnetostriction.
