Itinerant Ferromagnetism in the electronic localization limit

We present Hall effect, $R_{xy}(H)$, and magnetoresistance, $R_{xx}(H)$, measurements of ultrathin films of Ni, Co and Fe with thicknesses varying between 0.2-8 nm and resistances between 1 M$\mathrm{\Omega }$ - 100 $\mathrm{\Omega }\mathrm{.}$ Both measurements show that films having resistance above a critical value, $R_C$, (thickness below a critical value, $d_C$) show no signs for ferromagnetism. Ferromagnetism appears only for films with $R<R_C$, where $R_C$ is material dependent. We raise the possibility that the reason for the absence of spontaneous magnetization is suppression of itinerant ferromagnetism by electronic disorder in the strong localization regime.