Quasparticle spin susceptibility in heavy-fermion superconductors : An NMR study compared with specific heat results

Quasiparticle spin susceptibility (χ qp ) for various heavy-fermion (HF) superconductors is discussed on the basis of the experimental results of NMR Knight shift ( K ), NMR relaxation rate (1/ T 1 ), and electronic specific heat (γ el ) within the framework of the Fermi liquid model for a Kramers doublet crystal electric field (CEF) ground state. χ γ is calculated from the enhanced Sommerfeld coefficient γ el , and χ T 1 from the quasiparticle Korringa relation T 1 T ( K T 1 ) 2 =const. via the relation of χ T 1 =( N A µ B / A hf ) K T 1 where A hf is the hyperfine coupling constant, N A the Abogadoro's number and µ B the Bohr magneton. For the even-parity (spin-singlet) superconductors CeCu 2 Si 2 , CeCoIn 5 and UPd 2 Al 3 , the fractional decrease in the Knight shift, δ K obs = K obs ( T c )- K obs ( T →0), below the superconducting transition temperature ( T c ) is due to the decrease of the spin susceptibility of heavy quasiparticle estimated consistently from χ γ and χ T 1 . This result allows us to...