Münster 1999 – wissenschaftliches Programm

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AM: Magnetismus

AM 5: Legierungen der Übergangsmetalle, intermetallische Phasen, unterkühlte Metallschmelzen

AM 5.2: Vortrag

Montag, 22. März 1999, 17:15–17:30, F5

Observation of temperature induced low-spin to high-spin transitions in anti-Invar by paramagnetic neutron diffraction experiments — •M. Acet¹, E.F. Wassermann¹, A.P. Murani², and K.H. Andersen² — ¹Experimentelle Tieftemperaturphysik, Gerhard-Mercator-Universität Duisburg, 47048 Duisburg. — ²ILL, F-38042 Grenoble

The anti-Invar effect occuring in fcc Fe and its alloys is expected to be caused by transitions from a small volume low-spin state to a large volume high-spin state with increasing temperature. Fe_76.8Ni_13.3Mn_6.8C_3.2 is an anti-Invar material which is fcc down to low temperatures and therefore, provides a broad temperature range to study the anti-Invar effect. Paramagnetic neutron diffraction experiments with polarization analysis were carried out on this sample in the temperature range 4K≤T≤1200 K. Magnetic scattering in the foreward direction, indicating the presence of ferromagnetic correlations, strengthens with increasing temperature, although the ground state of the fcc phase is observed to be a spin glass with mixed ferromagnetic and antiferromagnetic correlations. The results give a clear identification of the thermally induced low-spin to high-spin transitions.
Work was supported by DFG within SFB166, Krupp VDM, and ILL Grenoble.