Wang, L.; Wei, L.; Shen, Z.; Wang, T.; Yao, R.; Wang, Z.; Luo, C.; Radu, F.; Gan, Y.; Chen, K.; Liao, Z.: Trigonal distortion and orbital polarization of Co2+ in a honeycomb cobaltate film grown on a SrTiO3 substrate. Physical Review B 112 (2025), p. 024428/1-9
10.1103/v9wr-1lgy
Abstract:
High-quality single-crystal films of CoTiO3 were fabricated on a SrTiO3 substrate using pulsed laser deposition methods, allowing for a detailed investigation of the electronic structure and orbital occupancy via x-ray linear dichroism in both in-plane and out-of-plane configurations. The combination of measurements and semiempirical calculations revealed that the trigonal distortion of CoO6 octahedra deviating from the cubic crystal field gives rise to an additional trigonal crystal field of Δtrig=45meV, with a low-lying 𝑒𝜋𝑔 orbital of the energetic splitting of the 𝑡2𝑔 band. Additionally, the x-ray magnetic circular dichroism (XMCD) at the Co 𝐿2,3 edge captured significant magnetic anisotropy and unquenched orbital angular momentum inherent in the film. An in-plane exchange field of −0.65 meV is required in the multiplet simulation to well reproduce the XMCD spectra obtained with field applied in the in- and out-of-plane directions. These findings provide insights into the potential of CoTiO3 to align with the Kitaev model when it is presented as a thin film, which is crucial for the further realization of quantum spin liquids via strain engineering.