Spin Waves in 3d Metals

A review is given of recent measurements of spin‐wave dispersion relations of the 3d metals by the Brookhaven neutron diffraction group using the diffraction technique and triple‐axis spectrometry. The parameters $D$ and $\beta$ in the relation ${\mathrm{ħ\omega \hspace{0.17em}=\hspace{0.17em}Dq}}^2{\text{(1\hspace{0.17em}−\hspace{0.17em}βq}}^2)$ have been determined at 295°K for Fe, Co, Ni, and some of their alloys. These values are compared with those obtained by thin‐film resonance and small‐angle scattering. The most extensive measurements were carried out on Fe using a triple‐axis spectrometer. The dispersion relation was measured along the three principal symmetry directions for wavevectors up to ${\mathrm{q/q}}_{\max }\text{\hspace{0.17em}=\hspace{0.17em}0.4}$ . The stiffness constant $D$ as well as the linewidth of selected spin waves were studied for the temperature range between 77°K and the Curie temperature, 1042°K. Well‐defined magnons were observed up to a reduced temperature ${\mathrm{T/T}}_{\mathrm{C}}\text{\hspace{0.17em}=\hspace{0.17em}0.995}$ , but not above $T_{\mathrm{C}}$ .