Phonon spectrum of the ferromagnetic superconductor UGe${}_2$ : Consequences for the specific heat

Abstract

We report inelastic neutron scattering measurements of the phonon spectrum of the pressure-induced ferromagnetic superconductor UGe${}_2$. No changes of the spectrum were found on cooling down to low temperature. The phonon contribution to the specific heat was estimated from a fit to our data. The excess specific heat previously noted at around $T_x\approx$ 30 K is not due to phonons but is well described by the temperature dependence of the magnetic order parameter at the molecular field level.

This paper has been withdrawn by the author due to a crucial error in phonon branches assignement