Comment on the isotope effect in weak itinerant ferromagnets

Abstract

The isotope effect on the Curie temperature is evaluated using our recent disscussion of the phonon contribution to the Stoner enhancement factor. An isotope effect exists only if the phonon contribution to the short-range Hubbard-type exchange interaction contains the small Migdal factor. The value of $\alpha =\left(\frac{M}{T_C}\right)\left(\frac{d{T}_C}{\mathrm{dM}}\right)$ is ≈ 1 or ≪ 1 depending on whether or not the phonon contribution is pertinent for the magnetic transition.