Quantum criticality in YbCu4Ni

We report on the quantum criticality of YbCu4Ni as revealed by our combined micro- and macromeasurements. We determine the crystal structure of YbCu4Ni with site mixing by neutron diffraction measurements, which suggests the possible presence of Kondo disorder. However, decreasing the local spin susceptibility distribution and the development of spin fluctuations below 10 K at ambient pressure by muon spin rotation and relaxation measurements suggests that YbCu4Ni exhibits quantum criticality. Therefore, our experimental results indicate that YbCu4Ni is a material that exhibits quantum criticality under zero magnetic field and ambient pressure.