Electron Spin Resonance Properties of CrI3 and CrCl3 Single Crystals

Developing functional, cleavable two-dimensional materials for use in next generation devices has recently become a topic of considerable interest due to their unique properties. Of particular interest, transition metal halides CrI3 and CrCl3 have shown to be good contenders for tunable and cleavable magnetic materials due to their unique magnetic properties in the monolayer. Here, electron spin resonance spectroscopy is used to pinpoint the atomic origins and underlying mechanisms of magnetic interactions as a function of temperature (5-500 K) and microwave frequency (9.43, 120 GHz) on CrI3 and CrCl3 bulk single crystals. ESR signals from CrI3 due to Cr3+ were observed to decay at 460 K, while ESR signals from CrCl3 remain up to 500 K. In the case of CrCl3, the temperature dependences of signal behavior, line width and g-value show characteristic signatures of ferromagnetic fluctuations at around 40 K, near to the antiferromagnetic phase transition at 17 K.