Magnetic field-induced orbital order in TbB2C2 observed by inelastic neutron scattering

摘要

Quadrupole (orbital) order in TbB2C2 has been investigated with inelastic neutron scattering (INS). TbB2C2 orders antiferromagnetically below T-N = 21.7 K and it has been proposed that antiferroquadrupolar (AFQ) order is induced with applied magnetic field. A broad magnetic excitation has been observed at 3.5 meV in zero fields. The AFQ order is witnessed through a strong shift of this low-lying excitation towards higher energy, while its intensity vanishes simultaneously. The Tb 4f wavefunctions are altered significantly, indicating directly that quadrupolar order is established. (c) 2005 Elsevier B.V. All rights reserved.