Small-angle interband scattering as the origin of the $T^{3/2}$ resistivity in MnSi

Abstract

A possible explanation is given for the anomalous $T^{3/2}$ temperature dependence of the electrical resistivity of MnSi, which is observed in the high-pressure paramagnetic state. The unusual Fermi surface of MnSi includes large open sheets that intersect along the faces of the cubic Brillouin zone. Close to these intersections, long-wavelength interband magnetic spin fluctuations can scatter electrons from one sheet to the other. The current relaxation rate due to such interband scattering events is not reduced by vertex corrections as is that for scattering from intraband ferromagnetic fluctuations. Consequently, current relaxation proceeds in a manner similar to that occurring in nearly antiferromagnetic metals, in which low-temperature $T^{3/2}$ behavior is well known. It is argued that this type of non-Fermi-liquid behavior can, for a metal with ferromagnetic fluctuations near Fermi sheet intersections, persist over a much wider temperature range than it does in nearly antiferromagnetic metals.