HIGH-RESOLUTION INELASTIC NEUTRON-SCATTERING FROM RBMNCMG1-CF3 (C=0.10 AND 0.15) UNDER MAGNETIC-FIELDS

Recently, a high-resolution inelastic neutron spectrometer equipped with a superconducting magnet has been installed at the pulsed spallation neutron source (KENS) at the National Laboratory for High Energy Physics (KEK). For the first experiment using this spectrometer system, we investigated inelastic neutron scattering from diluted Heisenberg magnetic systems, RbMncMg1-cF3 (c=0.10 and 0.15) at 1.5 K with applied magnetic fields. Magnetic excitations in finite-size clusters were observed due to the low concentration of spins localized at the manganese ions. The observed spectra were compared with calculations which were performed by diagonalizing the Hamiltonian. Extending the number of spins in a cluster up to five, good agreement with calculations was obtained for both excitation energies and scattering intensities.