Magnetic excitations in the itinerant antiferromagnets Mn3Si and Fe-doped Mn3Si.

Abstract

Magnetic excitations in the itinerant antiferromagnets Mn/sub 3/Si and Fe-doped Mn/sub 3/Si have been measured at low temperatures by inelastic scattering of neutrons. Mn/sub 3/Si is an incommensurate antiferromagnetic with magnetic Bragg points of the form (h,k,l) +- (delta,delta,delta) with delta = 0.425. Fe-doped Mn/sub 3/Si is a commensurate antiferromagnet with delta = (1/2. Its low-energy magnetic excitations have a linear dispersion relation with a slope of approximately 30 meV A, but above 6 meV, the slope increases so that the ''cone'' of the dispersion relation becomes a ''chimney.'' Well-defined excitations have been observed at energies up to 7.5k/sub B/T/sub N/ (15 meV). In pure Mn/sub 3/Si, a similar dispersion cone exists around each satellite magnetic Bragg point with a slope of approximately 37 meV A. The two dispersion cones from a pair of satellite points intersect at about 5 meV. Above this energy the intensity of the inelastic peaks changes drastically, indicating a strong interaction between the cones. For both phases, the damping is very large and increases almost linearly with energy.