Magnetic excitations in the half-metallic NiMnSb ferromagnet: From Heisenberg-type to itinerant behaviour

Magnetization, transport and inelastic neutron scattering experiments were performed on single crystals of the half metallic ferromagnet NiMnSb. A change in behaviour is observed near 80 K in the temperature dependence of magnetization and resistivity. Magnons were followed up to excitation energies of 70 meV, where they become overdamped due to the crossing of a Stoner mode. The magnetic behaviour seems to evolve from Heisenberg-like at low energies and low temperatures to itinerant magnetism at high temperatures and high excitation energies.