V-51 NMR and magnetic susceptibility study of the strong-coupling superconductor HfV2 - art. no. 024509

The Knight shift K of V-51 and the magnetic susceptibility chi in the C15 L aves phase compound HfV2 have been measured to investigate the change in th e electronic state at the martensitic lattice transformation temperature T- L and the symmetry of the superconducting order parameter. In the normal st ate, the hyperfine fields have been estimated to be -250 and - 72 kOe/mu (B ) above and below T-L, respectively. The reduction in the magnitude of hype rfine field is considered to be due to a strong s-d mixing induced by the l attice transformation. Above T-L the V 3d derived density of states N-3d(ep silon (F)) Obtained fi om K and the spin-lattice relaxation rate 1/T1T is c omparable with that estimated by a band calculation. The Knight shift due t o 3d spin vanishes well below the superconducting transition temperature T- c. Since the T-5 dependence of 1/T-1 well below T-c is explained by the ani sotropic energy gap that has nodes at points on the Fermi surface, the Coop er pair is thought to be of Anderson-Brinkman-Morel d gamma or d epsilon wa ve, for example.