Effect of Nonlocality on the Spin Correlations in Ferromagnetic Superconductors

Abstract
The dipole and Ruderman-Kittel-Kasuya-Yosida interactions between impurity spins in a superconductor are suppressed at long wavelengths. This results in a maximum in the neutron scattering at a temperature-independent wave number. It is essential to use nonlocal theory for the diamagnetic screening by the superconducting electrons. The local London approximation affects the neutron scattering cross section and overestimates the spin fluctuation energy by one order of magnitude.