Dresden 2003 – wissenschaftliches Programm

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SYEC: Materials under extreme conditions

SYEC 3: Extreme Conditions (Poster Session)

SYEC 3.3: Poster

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

P/T dependence of the phonon density of states in Fe₆₅Ni₃₅ Invar — •Hubertus Giefers¹, Kirsten Rupprecht¹, Ulrich Ponkratz¹, Olaf Leupold², and Gerhard Wortmann¹ — ¹Department of Physics, University of Paderborn, D-33095 Paderborn, Germany — ²ESRF, BP 220, F-38043 Grenoble, France

Fe₆₅Ni₃₅ is an archetype for an Invar alloy with a very low thermal expansion up to the Curie temperature around 520 K [1]. Here we investigate Fe₆₅Ni₃₅ by nuclear inelastic scattering (NIS) of synchrotron radiation [2-5] which provides the (local) phonon density-of-states (DOS) at Fe, at 300 K and pressures up to 17 GPa as well as at ambient pressure in the temperature range 5 to 660 K. The pressure induced suppression of the Invar properties is sensitively monitored by a characteristic anomaly around 12 GPa in a variety of derived elastic parameters. In contrast to the pressure dependence, the temperature dependence of the phonon DOS is very weak in the temperature range 5 to 400 K, and only above 450 K characteristic changes [2] are observed. Information on the magnetic properties of Fe₆₅Ni₃₅ are presented in [6].

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

[2] A.I. Chumakov et al., Phys. Rev. B 54, R9596 (1996).

[3] R. Lübbers et al., Science 287, 1250 (2000).

[4] H.K. Mao et al., Science 292, 914 (2001).

[5] H. Giefers et al., High Press. Res. 22, 501 (2002).

[6] K. Rupprecht et al., contr. to this symposium.