Magnetic Field Dependent Low-Temperature Specific Heat in UCo_1-xFe_xGe

We have investigated low-temperature specific heat of UCo_1-xFe_xGe with x spanning a narrow region around the concentration x=0.23 of the purported Ferromagnetic Quantum Critical point (FM QCP), at temperatures from 60 mK to 2 K and in magnetic field up to 9 T. All investigated samples show a rise in specific heat at low temperature when external field is applied, interpreted as being due to the Co nuclear Schottky anomaly, as the magnitude of the low temperature anomaly scales with the Co content. The Schottky anomaly is absent when the external field is zero, and x is close to 0.23, indicating paramagnetic ground state in these samples. The shallow rise of the Sommerfeld coefficient γ= C/T with decreasing temperature for x=0.22 and x=0.23 samples is consistent with previously reported higher temperature specific heat data, which were interpreted as an evidence of an FM QCP. In this talk, we discuss about quantum criticality of UCo_1-xFe_xGe system.