Magnetic Field Dependence of the Spin Susceptibility on Conventional s-wave Superconductor LaRu${}_4$P${}_{12}$ Revealed by ${}^{31}$P-NMR and ${}^{139}$La-NMR

The magnetic field dependence of the spin part of Knight shift, which is proportional to the superconducting-state spin susceptibility, was investigated at two nuclear sites, ${}^{31}$P and ${}^{139}$La in a conventional s-wave superconductor LaRu${}_4$P${}_{12}$. After the analyses, we confirmed that the superconducting-state spin susceptibility is proportional to magnetic field, and connects to the normal-state spin susceptibility smoothly. This is a textbook example, when the superconductivity is broken with the orbital pair-breaking effect.