Dresden 2003 – wissenschaftliches Programm

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SYEC: Materials under extreme conditions

SYEC 3: Extreme Conditions (Poster Session)

SYEC 3.2: Poster

Mittwoch, 26. März 2003, 13:00–19:00, P2a

P/T dependence of magnetic properties in Fe₆₅Ni₃₅ Invar — •Kirsten Rupprecht¹, Hubertus Giefers¹, Gerhard Wortmann¹, Olaf Leupold², and Uwe van Bürck³ — ¹Fachbereich Physik, Universität Paderborn, D-33095 Paderborn, Germany — ²ESRF, BP 220, F-38043 Grenoble, France — ³Physik-Department E13, Technical University München, D-85747 Garching, Germany

Fe₆₅Ni₃₅ is an archetype for an Invar alloy with a very low thermal expansion up to the Curie temperature T_C around 520 K [1]. Here we investigated Fe₆₅Ni₃₅ by ⁵⁷Fe-Mössbauer spectroscopy (MS) as well as by nuclear forward scattering (NFS) of synchrotron radiation [2] at pressures up to 17 GPa and at temperatures up to 600 K. The NFS studies were performed simultaneously with nuclear inelastic scattering (NIS) studies, which provided the local phonon-DOS at Fe [3]. ⁵⁷Fe-NFS spectra, recorded at 300 K and pressures up to 17 GPa, indicated the reduction of T_C from about 520 K to about 300 K at a pressure of 5.3 GPa. Mössbauer spectra measured at various pressures up to 12.5 GPa from 4.2 K to 300 K provided information about the lowering of the magnetic ordering temperatures and of the reduction of the Fe magnetic hyperfine fields; similar to the results from a previous MS study up to 7 GPa [4].

[1] see E.F. Wassermann, J. Magn. Magn. Mat. 100, 346 (1991) and references therein.

[2] R. Lübbers, K. Rupprecht, G. Wortmann, Hyp. Interact. 128, 115 (2000); K. Rupprecht et al., High Pressure Research 22, 189 (2002).

[3] H. Giefers et al., contribution to this symposium.

[4] M.M. Abd-Elmeguid et al., J. Magn. Magn. Mat. 72, 253 (1988). Supported by the BMBF (05 KS1PPB/3).