The magnon dispersion curve of Gd metal has been determined from first principles by use of augmented-plane-wave energy bands and wave functions. The exchange matrix elements $I(\overrightarrow{\mathrm{k}}, {\overrightarrow{\mathrm{k}}}^{\prime })$ between the $4f$ electrons and the conduction electrons from the first six energy bands were calculated under the assumption of an unscreened Coulomb interaction. The results are in good overall agreement with experiment provided the $I(\overrightarrow{\mathrm{k}}, {\overrightarrow{\mathrm{k}}}^{\prime })$ are diminished by a constant scale factor of about 2 which may be caused by screening.

• Received 29 April 1975

DOI:https://doi.org/10.1103/PhysRevLett.35.383