Nature of the irradiation-induced low-temperature magnetic transition

Determine the precise nature of the approximately 40 K magnetic phase transition in He+ ion-irradiated CrSBr, including whether it arises from ferromagnetic ordering of irradiation-induced magnetic defects, spin freezing caused by suppressed spin fluctuations, or a crossover from XY to triaxial magnetic anisotropy.

Background

He+ irradiation of layered CrSBr produces anomalies in the temperature-dependent Raman tensor near 40 K and 105–110 K. The authors associate the higher-temperature anomaly with magnetic ordering from the paramagnetic state into a modified antiferromagnetic or ferromagnetic phase, whereas the lower-temperature anomaly is associated with irradiation-induced defects.

Because the defect concentration is dilute and exchange interactions act over atomic length scales shorter than the typical separation between defects, the physical mechanism of the approximately 40 K transition cannot be identified from the reported measurements. The paper therefore leaves unresolved whether the transition reflects defect-induced ferromagnetism, spin freezing, or a change in magnetic anisotropy.