Antiferromagnetic spin fluctuations in the heavy-fermion superconductor Ce ₂PdIn ₈

Inelastic neutron scattering and muon spin relaxation/rotation (μSR) measurements were performed on the heavy-fermion superconductor Ce ₂PdIn ₈. The observed scaling of the imaginary part of the dynamical susceptibility χ′′Tα∞f(ω/k _BT) with α=3/2 revealed a non-Fermi liquid character of the normal state, being due to critical antiferromagnetic fluctuations near a T=0 quantum phase transition. The longitudinal-field μSR measurements indicated that superconductivity and antiferromagnetic spin fluctuations coexist in Ce ₂PdIn ₈ on a microscopic scale. The observed power-law temperature dependence of the magnetic penetration depth λ∞T3 ^/2, deduced from the transverse-field μSR data, strongly confirms an unconventional superconductivity in this compound.