  In itinerant ferromagnets, the quenched disorder is predicted to dramatically
affect the ferromagnetic to paramagnetic quantum phase transition driven by
external control parameters at zero temperature. Here we report a study on
Fe-doped Cr$_2$B, which, starting from the paramagnetic parent, orders
ferromagnetically for Fe-doping concentrations $x$ larger than $x_{\rm
c}=2.5$\%. In parent Cr$_2$B, $^{11}$B nuclear magnetic resonance data reveal
the presence of both ferromagnetic and antiferromagnetic fluctuations. The
latter are suppressed with Fe-doping, before the ferromagnetic ones finally
prevail for $x>x_{\rm c}$. Indications for non-Fermi liquid behavior, usually
associated with the proximity of a quantum critical point, were found for all
samples, including undoped Cr$_2$B. The sharpness of the ferromagnetic-like
transition changes on moving away from $x_{\rm c}$, indicating significant
changes in the nature of the magnetic transitions in the vicinity of the
quantum critical point. Our data provide constraints for understanding quantum
phase transitions in itinerant ferromagnets in the limit of weak quenched
disorder.
