J. Phys. IV France 11 (2001) Pr8-269-Pr8-274
Anisotropic magnetic field-effect on martensitic transformation for Co and Co alloysT. Tanaka1, M. Takahashi2 and S. Kadowaki2
1 Department of Materials Science and Engineering, Ehime University, Matsuyama 790-8577, Japan
2 Department of Electronic Engineering, Tohoku University, Sendai 980-8579, Japan
The experimental evidences on the anisotropic field-induced martensitic transformation were summarized for the cases of the fcc-to-hcp, fcc-to-dhcp and dhcp-to-hcp martensitic trasformation in Co and Co alloys. In these phase transformations, the magnitude of the magnetic field as small as some kilo Oe was enough to induce the martensitic transformation and the magnetic field acted anisotropically. The magnetocIystalline anisotropy energy was explained as the main motive force of this anisotropic field-induced martensitic transformation from the thermo-dynamical consideration. The shear stresses regarding to the magnetostriction are estimated to be the same order of the reported value of the resolved shear stress for Co, and these shear stresses did not meet the experimental results concerning to the direction of the external field clearly. The shear stress together with the magnetostriction would play an important role on the formation of the nucleation site of the martensitic tansformation in the domain walls.
© EDP Sciences 2001