An electron-phonon contribution to the stoner enhancement in GaMo4X8 compounds

Using the Stoner-Wohlfarth model of itinerant ferromagnetism for GaMo₄X₈ compounds, we determine the electron-phonon enhancement from their electronic specific heats. These compounds have unstable structures due to strong electron-phonon coupling. The room-temperature structure can be stabilized by doping with nonmagnetic isoelectronic impurities. The Curie temperature is decreased by a factor of three as a consequence of itinerant-electron parallel-spin scattering on nonmagnetic impurities. This property demonstrates that a long-range ferromagnetic interaction contributes to the Stoner enhancement. We speculate that the amplitude of this extra contribution is governed by the electron-phonon coupling, which depends on the mass. We are able to predict the experimental values of and the amplitude of the possible isotope effect.