Observation Of A New Field-Induced Phase Transition And Its Concomitant Quantum Critical Fluctuations In Ceco(In1-Xznx)(5)

We demonstrate a close connection between observed field-induced antiferromagnetic (AFM) order and quantum critical fluctuation (QCF) in the Zn7%-doped heavy-fermion superconductor CeCoIn5. Magnetization, specific heat, and electrical resistivity at low temperatures all show the presence of new field-induced AFM order under the magnetic field B of 5-10 T, whose order parameter is clearly distinguished from the low-field AFM phase observed for B < 5 T and the superconducting phase forB < 3 T. The 4f electronic specific heat divided by the temperature, C-e/T, exhibits - ln T dependence at B similar to 10 T (equivalent to B-0), and furthermore, the C-e/T data for B >= B-0 are well scaled by the logarithmic function of B and T : ln[(B - B-0)/T-2.7]. These features are quite similar to the scaling behavior found in pure CeCoIn5, strongly suggesting that the field-induced QCF in pure CeCoIn5 originates from the hidden AFM order parameter equivalent to high-field AFM order in Zn7%-doped CeCoIn5.