Metal-insulator transition and magnetic fluctuations in polycrystalline Ru1−xRhxP investigated by P31 NMR

Abstract

$^{31}\mathrm{P}$ NMR measurements have been made on polycrystalline samples to study a metal-insulator (MI) transition and magnetic fluctuations in ${\mathrm{Ru}}_{1\ensuremath{-}x}{\mathrm{Rh}}_{x}\mathrm{P}$ which has metallic (M), pseudogap (PG), insulating (I), and superconducting (SC) phases. We find that RuP undergoes a crossover from the high-temperature (high-$T$) M phase to the PG phase with the pseudo spin-gap behavior probed by the nuclear spin-lattice relaxation rate at ${T}_{\mathrm{PG}}=330\phantom{\rule{4pt}{0ex}}\mathrm{K}$. The first-order MI transition is observed to take place from the PG phase to the low-$T$ nonmagnetic I phase with the spin-gap energy of 1250 K at ${T}_{\mathrm{MI}}=270\phantom{\rule{4pt}{0ex}}\mathrm{K}$. In the PG phase of ${\mathrm{Ru}}_{1\ensuremath{-}x}{\mathrm{Rh}}_{x}\mathrm{P}$ with $0\ensuremath{\le}x<0.45$, an analysis based on the modified Korringa relation, which is applicable to an itinerant paramagnet with weak electron correlation, shows that antiferromagnetic (AFM) fluctuations described in the random-phase approximation are enhanced in the low-$T$ and low-$x$ region. Around the PG-M phase boundary at ${x}_{\mathrm{c}}\ensuremath{\sim}0.45$, there is the SC phase whose normal state has negligible electron-electron interaction. We discuss the MI transition, the crossover from the M phase to the PG phase, and the magnetic properties of each phase based on the band structure.