This paper reports investigation of the role of spin fluctuations (paramagnons) in the superconductors Nb and V. For this purpose, experimental data on specific heat and magnetic susceptibility are reanalyzed. Furthermore, the Eliashberg equations including the particle-hole $t$ matrix are solved numerically. It is found that in Nb and V, spin fluctuations substantially reduce $T_c$, while their contribution to the mass enhancement $\frac{m^{*}}{m}$ is typically of order 0.2.

• Received 5 July 1979

DOI:https://doi.org/10.1103/PhysRevLett.43.1256