H∕T scaling in disordered non-Fermi liquid materials Ce(Ru_1−xRh_x)₂Si₂ for x=0.5 and 0.6: Quantum Griffiths nature

Low field ac-susceptibility experiments have been carried out to study the effect of “chemical” disorder and proximity to a magnetic quantum critical point (QCP) on the non-Fermi liquid (NFL) behavior in Ce(Ru_1−xRh_x)₂Si₂ for x=0.5 and 0.6 and CeCu_5.9Au_0.1. The susceptibility of strongly disordered NFL material Ce(Ru_1−xRh_x)₂Si₂ contains two components associated with different mechanisms; a disorder-driven component δχ and a mean-field (MF) quantum critical component χ_MF. δχ exhibits H∕T-scaling in the form of T^−γf(H∕T) with γ depending on x. In contrast, the disorder-driven component has not been observed in weakly disordered NFL material CeCu_5.9Au_0.1. The results of the scaling analysis strongly suggest that δχ is due to the quantum Griffiths singularity.