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Abstract:
Cr2B displays temperature-independent paramagnetism. We induce
ferromagnetism by replacing less than 3% of the Cr atoms by Fe. By the
lowest Fe doping level made, Curie-Weiss behavior is observed; Theta(CW)
changes from -20 K for 0.5% Fe-doped Cr2B to positive values of about 50
K by 5% Fe doping. The ferromagnetic T-C is 8 K for 2.5% Fe doping and
increases linearly to 46 K by 5% doping; we infer that a quantum phase
transition occurs near the 2.0% Fe level. Magnetic fluctuations at the
intermediate doping levels are reflected in the linear resistance and an
anomalous heat capacity at low temperatures. Imaging and chemical
analysis down to the atomic scale show that the Fe dopant is randomly
distributed.
