Crystal-field transitions of Nd ions in a triangular antiferromagnetic lattice

We propose an inelastic neuron scattering experiment to measure crystal-field transitions in the layered frustrated magnet CuNdO2. Here Kramers Nd3+ ions with effective spin-1/2 form a triangular lattice with frustrated antiferromagnetic couplings (filled-shell Cu+ ions are non-magnetic). We have a well-characterized powder sample where thermodynamic measurements evidence onset of long-range magnetic order below 0.8 K with a Curie-Weiss temperature of -3.6 K. Crystal-field calculations using an approximate point-charge model, which is in general a good starting point for the crystal field of rare-earth ions, predict 5 Kramers doublets spanning an energy range of around 110 meV, so we apply for MERLIN beamtime to study such crystal-field transitions and determine the appropriate spin-orbital ground state. The interest in this system is motivated by research on Nd3+ ions in similar crystal-field environments which suggest an Ising-like character, which would make the present material an ideal candidate to explore the physics of Ising frustration in the presence of sizeable exchange interactions, where the excitations spectrum could also be probed experimentally, in contrast to other candidate Ising triangular systems where the interaction scale is an order of magnitude smaller and therefore experimentally not accessible with current INS spectrometers.