Spin-Wave Excitations in the Conical and Spiral Magnetic Phases of Holmium Metal

Abstract

Spin-wave excitations propagating along the c and a axes of holmium metal have been studied by neutron inelastic scattering techniques, with a triple-axis spectrometer in both the constant Q and constant energy-transfer modes of operation. Measurements were made in the conical magnetic phase at a temperature of 4.6°K and in the spiral phase at 25°K. The dispersion curves for the two phases are similar in shape, although the spin-wave energies in the spiral phase are consistently lower than in the conical phase. For example, the energies of spin waves of wave vector (0, 0, 2π/c) are 3.97±0.21 and 3.48±0.21 meV in the conical and spiral phases, respectively, while those of spin waves of wave vector (0, 0, π/c) are 2.64±0.21 and 2.07±0.17 meV, respectively. The results give information about the Fourier-transformed exchange, J(0)−J(q), and the crystal field parameters.