Electron-phonon coupling in M n1-x F exSi

We present a study of the lattice dynamical properties of Mn1-xFexSi with 0≤x≤0.22. Employing time-of-flight neutron spectroscopy and inelastic x-ray scattering, we investigate the doping dependence of phonon energies, Eph, and linewidths, Γph. We find anomalous softening and broadening of a phonon mode propagating along the [111] direction. Ab initio lattice dynamical calculations link this softening to an enhanced electron-phonon coupling due to the doping-dependent changes of the Fermi surface. We discuss an interplay of increased electron-phonon coupling and reduced ordered magnetic moments in Mn1-xFexSi.