Hyperfine Couplings as a Probe of Orbital Anisotropy in Heavy Fermion Materials

Abstract

The transferred hyperfine interaction between nuclear and electron spins in an heavy fermion material depends on the hybridization between the $f$-electron orbitals and those surrounding a distant nucleus. In CeMIn${}_5$ (M=Rh, Ir, Co), both the hyperfine coupling to the two indium sites as well as the crystalline electric field at the Ce are strongly dependent on the transition metal. We measure a series of CeRh${}_{1-x}$Ir${}_x$In${}_5$ crystals and find that the hyperfine coupling reflects the orbital anisotropy of the ground state Ce 4$f$ wavefunction. These findings provide direct proof that the localized to itinerant transition is dominated by hybridization out of the Ce-In plane in this system.

10 pages, 11 figures