Quantifying the evolution of quantum interactions in CrCl₃, a van der Waals magnet, from paramagnetic to ferromagnetic phases.

In 2D van der Waals (vdW) magnetic material, quantum interactions, such as exchange interactions between neighboring spins, encourage them to align in a particular way (ferromagnetically or antiferromagnetically). These interactions ultimately shape the control over magnetic phase transitions between different ordered states, like ferromagnetic (FM) and antiferromagnetic (AFM). They also influence magnetization dynamics and emergent phenomena, such as topological order and quantum fluctuations in the 2D limit. In this talk, we will discuss how the exchange and dipolar interactions evolve as CrCl₃, a layer vdW magnet, transitions from paramagnetic to ferromagnetic phases. We utilized broadband magnetic resonance and the Anderson–Weiss model ^[1-2] to quantify the exchange (Hₑₓ) and dipolar (H_d) interactions. Our measurement showed that the exchange interaction (H_ex) changes from 40 mT at room temperature to 85 mT at 14 K ^[4]. However, the dipolar interaction (H_d) changes from 5 mT to 15 mT ^[4] within the same temperature range. We estimate that the exchange interaction in the antiferromagnetic phase at 7K would be 90mT, which is in agreement with the literature value ^[3]. [1] P. W. Anderson and P. R. Weiss, Rev. Mod. Phys. 25, 269 (1953), [2]. Brant Cage et al., JMR 135, 178 (1998), [3] D. MacNeill, et al Phys. Rev. Lett. 123, 047204 (2019).[4] P. B. Karki, et al., under preparation.