Spin-orbit exciton in a honeycomb lattice magnet CoTiO3: Revealing a link between magnetism in d- and f-electron systems

We carried out inelastic neutron scattering to study the spin-orbit (SO) exciton in a single crystal sample of CoTiO3 as a function of temperature. CoTiO3 is a honeycomb magnet with dominant XY-type magnetic interaction and an A-type antiferromagnetic order below TN≈38 K. We found that the SO exciton becomes softer but acquires a larger bandwidth in the paramagnetic phase, compared to that in the magnetically ordered phase. Moreover, an …