Paramagnetic to ferromagnetic phase transition in lightly Fe-doped Cr2B.

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; ϴCW changes from –20 K for 0.5% Fe-doped Cr2B to positive values of about 50 K by 5% Fe doping. The ferromagnetic TC 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. [ABSTRACT FROM AUTHOR]