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Abstract:
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 Cr2B, which, starting from the
paramagnetic parent, orders ferromagnetically for Fe-doping
concentrations x larger than x(c) = 2.5%. In parent Cr2B, B-11 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(c).
Indications for non-Fermi-liquid behavior, usually associated with the
proximity of a quantum critical point, were found for all samples,
including undoped Cr2B. The sharpness of the ferromagneticlike
transition changes on moving away from x(c), indicating significant
changes in the nature of the magnetic transitions in the vicinity of the
quantum critical point. Our data provide some constraints for
understanding quantum phase transitions in itinerant ferromagnets in the
limit of weak quenched disorder.
