Temperature dependence of spin fluctuation scattering of neutrons on pyrrhotite

Abstract

By means of the triple axis Cracow neutron spectrometer installed at Vinca (Yugoslavia), coherent inelastic scattering of monochromatic neutrons (λ0 = 1.376 Å) connected with τ = (001) was investigated at various temperatures above room temperature up to 400 °C, i.e. above the critical point (TN = 320 °C) of the spin alignment in pyrrhotite. The intensity of the (001) scattering cone increases with temperature but its magnon character does not change. Only at temperatures above 200 °C do the widths of the magnon peaks begin to increase. This temperature is not very sensitive to the energy of a given magnon group. The high degree of inelasticity is maintained over the critical point region and the mean energy transfer is close to the one for low temperatures. The results are discussed in terms of magnon lifetime and temperature dependence of effective exchange coupling