A neutron-scattering investigation of the magnetic structure and magnetic excitations in nanocrystalline Tb

The magnetic structure and magnetic excitations in nanocrystalline Tb have been investigated by neutron diffraction and neutron spectroscopy. This is a report on the long-range magnetic order and the magnetic excitations in a nanocrystalline elemental rare earth. Refinement of the neutron-diffraction data reveals an “average” magnetic structure of each crystallite which contains a significant out-of-plane component to the magnetic moment as well as a suppression of the high-temperature antiferromagnetic phase observed for coarse-grained Tb. The inelastic-neutron-scattering measurements reveal the presence of a magnetic excitation of approximately 10 meV at 2.5 K. The excitation energy decreases with increasing temperature. The origins of this excitation are discussed with particular reference to the magnetic modes at the zone center observed for single-crystal Tb.