Itinerant ferromagnetism in the electronic localization limit

We present Hall effect, Rxy(H), and magnetoresistance, Rxx(H), measurements of ultrathin films of Ni, Co, and Fe with thicknesses varying between 0.2 and 8 nm and resistances between 1MΩ and 100Ω. Both measurements show that films having a resistance above a critical value RC, (thickness below a critical value, dC) show no signs of ferromagnetism. Ferromagnetism appears only for films with R<RC, where RC is material dependent. We raise the possibility that the reason for the absence of spontaneous magnetism is the suppression of itinerant ferromagnetism by electronic disorder in the strong localization regime.