J. Phys. Colloques
Volume 42, Numéro C6, Décembre 1981International Conference on Phonon Physics
|Page(s)||C6-770 - C6-772|
J. Phys. Colloques 42 (1981) C6-770-C6-772
SOFT PHONONS AND MAGNETIC ORDERING IN THE γ-PHASE TRANSITION METAL ALLOYS Fe1-xPdxM. Sato1, B.H. Grier2, S.M. Shapiro2 et H. Miyajima1
1 The Institute for Solid State Physics, the University of Tokyo, Roppongi, 7-22-1, Minato-ku, Tokyo 106, Japan
2 Brookhaven National Laboratory, Upton, New York 11973, U.S.A.
Neutron inelastic scattering measurements have been performed on two single crystals of the thermally quenched γ-phase (fcc) alloy, Fe1-xPdx with x = 0.28 and x = 0.37. The x = 0.28 sample which orders ferromagnetically at Tc = 575 K exhibits a smeared structural transition into an fct phase near TM = 265 K. An anomalous dispersion of the [ζζ0]TAl branch due to the decrease of the phonon energy around the Ɖ point develops below Tc. As the temperature decreases, the branch decreases in energy. The anomalous part of the elastic constant, Ɗ(C11-C12)/2, follows the same temperature dependence as the square of the magnetization. On the x = 0.37 sample which has no structure transition, the phonon anomaly is much weaker. For both crystals the other branches exhibit normal behavior.