Pathiraja, C.S.; Ranhili, J.N.; Wong, D.; Schulz, C.; Chuang, Y.-D.; Shao, Y.-C.; Huang, D.-J.; Huang, H.-Y.; Singh, A.; Freelon, B.: Electronic energy scales of CrX3 (X = Cl, Br, and I) using high-resolution x-ray scattering. Physical Review Research 7 (2025), p. 043139/1-10
10.1103/jdxn-5lw4
Open Access Version
Abstract:
Chromium trihalides Cr𝑋3 (𝑋=Cl, Br, and I) have recently become a focal point of research due to their intriguing low-temperature, layer-dependent magnetic properties that can be manipulated by external stimuli. This makes them essential candidates for spintronic applications. Their magnetic orders are often related to the electronic structure parameters, such as spin-orbit coupling (SOC), Hund’s coupling (𝐽𝐻), 𝑝−𝑑 covalency, and interorbital Coulomb interactions. Accurately determining such parameters is paramount for understanding Cr𝑋3 physics. We have used high-resolution resonant inelastic x-ray scattering spectroscopy to study Cr𝑋3 across phase transition temperatures. Ligand field multiplet calculations were used to determine the electronic structure parameters by incorporating the crystal field interactions in a distorted octahedral orientation with 𝐶3 symmetry. These methods provide the most detailed description of Cr𝑋3 magneto-optical and electronic (energetic) terms to date. The crystal field distortion parameters 𝐷𝜎 and 𝐷𝜏 were experimentally determined, and the energies of 𝑑 orbitals have been reported. The spectroscopic measurements reveal an energy separation between spin-allowed quartet states and spin-forbidden doublet states, which increases upon going from CrCl3 to CrI3. The role of SOC, for Cr 2𝑝 orbitals, in spin-flip excitations has been demonstrated. The determined 10𝐷𝑞 values are in good agreement with the spectrochemical series, and Racah 𝐵 follows the nephelauxetic effect. Such precise measurements offer insights into the energy design of spintronic devices that utilize quantum state tuning within two-dimensional magnetic materials.