Neutron scattering measurements of phonons in iron above and belowTc

We report detailed measurements of transverse phonons in Fe propagating along the [110] direction with [11¯0] polarization, both above and below $T_c$. The low-q measurements give the elastic constant C’, which decreases anomalously as $T_c$ is approached from below, in agreement with the ultrasonic measurement. Phonon-frequency measurements throughout the Brillouin zone show a kink in the vicinity of $T_c$, thus indicating their magnetoelastic origin.