Quantum critical behavior of disordered itinerant ferromagnets

The quantum ferromagnetic transition at zero temperature in disordered itinerant electron systems is considered. Nonmagnetic quenched disorder leads to diffusive electron dynamics that induces an effective long-range interaction between the spin or order parameter fluctuations of the form $r^{2-2d}$, with $d$ the spatial dimension. This leads to unusual scaling behavior at the quantum critical point, which is determined exactly. In three-dimensional systems the quantum critical exponents are substantially different from their finite-temperature counterparts, a difference that should be easily observable. Experiments to check these predictions are proposed.