Magnetic Secondary Phases in the Annealed van der Waals Antiferromagnet CrSBr

The van der Waals semiconductor CrSBr combines tunable electronic transport, two-dimensional magnetism with a low critical switching field, and stability at ambient conditions, making it an interesting material for fundamental studies of low-dimensional properties and for spintronic device engineering. Recent studies have revealed two magnetic transitions well below the 132 K Néel temperature: an additional magnetic order that affects magnetotransport below 30 K, and an increase in the bulk magnetic susceptibility below 40 K. Here we demonstrate that the feature apparent in the susceptibility below 40 K is caused by CrBr3 secondary-phase impurities unrelated to the magnetic ordering observed below 30 K. We study the effects of annealing CrSBr single crystals at a range of temperatures, and we demonstrate that annealing above 800 °C establishes the secondary phases Cr2S3 and CrBr3, both of which exhibit magnetic signatures distinct from that of CrSBr. Our results suggest that annealing treatments may be used to improve the purity of as-synthesized CrSBr single crystals or to tune their magnetic properties through the formation of magnetic secondary phases.