Quantum critical spin-liquid-like behavior in the S= 12 quasikagome-lattice compound CeRh1-x PdxSn investigated using muon spin relaxation and neutron scattering

We present the results of muon spin relaxation (μSR) and neutron scattering on the Ce-based quasikagome lattice CeRh1-xPdxSn (x=0.1 to 0.75). Our zero-field (ZF) μSR results reveal the absence of both static long-range magnetic order and spin freezing down to 0.05 K in the single-crystal sample of x=0.1. The weak temperature-dependent plateaus of the dynamic spin fluctuations below 0.2 K in ZF-μSR together with its longitudinal-field (LF) dependence between 0 and 3 kG indicate the presence of dynamic spin fluctuations persisting even at T=0.05K without static magnetic order. On the other hand, the magnetic specific heat divided by temperature C4f/T increases as -logT on cooling below 0.9 K, passes through a broad maximum at 0.13 K, and slightly decreases on further cooling. The ac susceptibility also exhibits a frequency-independent broad peak at 0.16 K, which is prominent with an applied field H along the c direction. We, therefore, argue that such a behavior for x=0.1 [namely, a plateau in spin relaxation rate (λ) below 0.2 K and a linear T dependence in C4f below 0.13 K] can be attributed to a metallic spin-liquid-like ground state near the quantum critical point in the frustrated Kondo lattice. The LF-μSR study suggests that the out of kagome plane spin fluctuations are responsible for the spin-liquid (SL) behavior. Low-energy inelastic neutron scattering (INS) of x=0.1 reveals gapless magnetic excitations, which are also supported by the behavior of C4f proportional to T1.1 down to 0.06 K. Our high-energy INS study shows very weak and broad scattering in x=0 and 0.1, which transforms into well-localized crystal-field excitations with increasing x. The ZF-μSR results for the x=0.2 polycrystalline sample exhibit similar behavior to that of x=0.1. A saturation of λ below 0.2 K suggests a spin-fluctuating SL ground state down to 0.05 K. The ZF-μSR results for the x=0.5 sample are interpreted as a long-range antiferromagnetic (AFM) ground state below TN=0.8K, in which the AFM interaction of the enlarged moments probably overcomes the frustration effect. The long-range AFM ordering is also supported by the evolution of magnetic Bragg peaks in x=0.75 sample observed below 5 K in the neutron diffraction data.