Temperature dependence of magnetic excitations in Pd3Fe

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Abstract
Measurements of the magnetic excitation spectrum of ferromagnetic Pd3Fe (Tc=499K) have been made at 293, 373, 423, 473 and 573K by neutron inelastic scattering techniques. Constant energy and constant momentum transfer modes of operation were employed with reduced wavevectors between 0.11 and 0.40 in the ( zeta 00) direction. At 293K a single branch of the dispersion relation for magnetic excitations is observed which is characterized by an exchange stiffness of 52.7+or-2.7 THz AA2. The intrinsic linewidth is a strong function of wave vector and varies from 0.0+or-0.5 THz at zeta =0.13 to 2.5+or-0.5 THz at zeta =0.30. When the temperature is raised the excitation frequencies fall and the linewidths increase. Between 293 and 473K at zeta =0.3 the frequency falls by a factor of 1.8 and the linewidth increases by the same factor, but a broad inelastic response is still observed. At 473K at wavevectors less than zeta =0.13, the magnetic scattering has the form of a peak of appreciable width centred on zero frequency.