Strong damping of field-induced quantum fluctuations in weak-coupling Kondo lattices: The case of YbNi4Cd

Quantum phase transitions in Kondo-lattice compounds generally arise from the competition between the Kondo effect and the Ruderman-Kittel-Kasuya-Yosida exchange interaction. Magnetic field is a convenient control parameter of the competition and can smoothly suppress the magnetic ordering to zero temperature at a quantum critical point (QCP), where singular electronic properties beyond Fermi liquid often emerge, reflecting the enhanced quantum critical fluctuations. Here, we provide experimental evidence that the antiferromagnetic compound YbNi4Cd, characterized by a weak Kondo coupling, can be tuned to QCP by applying a small field of less than 1 T. This tuning results in, however, no typical non-Fermi liquid behavior. Strong damping of quantum critical fluctuations in Zeeman field, which is comparable to the Kondo effect in this compound, is evidenced by low-temperature magnetic, specific-heat, and magnetocaloric effect measurements. Our findings are discussed as generic quantum critical characteristics of weak-coupling Kondo lattices, where the Kondo temperature is comparable to or smaller than the magnetic ordering temperature.