J. Phys. IV France 07 (1997) C5-401-C5-404
The Role of the Nature of Magnetic Coupling on the Martensitic Transformation in Fe-NiM. Acet1, E.F. Wassermann1, K. Andersen2, A. Murani2 and O. Schärpff2
1 Tieftemperaturphysik, Gerhard-Mercator Universität Duisburg, 47048 Duisbourg, Germany
2 Institut Laue-Langevin, BP. 156, 38042 Grenoble cedex 9, France
Fe100-xNix with x≤30 at.%, known as anti-Invar alloys, undergo martensitic transformations. Total energy calculations have shown that these alloys incorporate a strongly fluctuating magnetic moment in the fcc state. In order to understand the relationship between the moment fluctuations and the martensitic transformation, we have investigated the magnetic moment in the paramagnetic fcc state of these alloys by polarized neutron diffraction. We find that the magnetic correlations ar ferromagnetic in nature although, the ground state of these alloys are expected to be antiferromagnetic. We further observe that the magnetic moment of the fcc state at Ms increases with increasing Ni concentration, indicating that the fcc state is stabilized by increasing ferromagnetic exchange. The results are found to be in agreement with thermodynamical predictions.
© EDP Sciences 1997