Low-energy crystal field excitations observed using inelastic neutron scattering

Abstract

The time-of-flight spectrometer, PELICAN, at ANSTO operates two choppers which provide a fixed initial energy of neutrons to the sample. Configuring the instrument to a wavelength of 4.75Å, sets this initial neutron energy to 3.6meV. By phasing the choppers, however, harmonic wavelengths can be obtained such as λ/2, etc. By measuring a powder sample of ErNiAl4 at λ/2 (λ = 4.75Å) we could observe a greater range of positive energy transfers (to the sample) and, after appropriate background removal, confirm the presence of an excitation at 7meV. This excitation represents the emission from the crystal field level at 7meV to 0meV confirming the result obtained in a previous experiment.