Fig. 4. Properties of CrSBr monolayer near T = T_N.

a Magnetic field image of Sample S2_Encap at T = 130K with a bias magnetic field (B_ext = 5mT applied along the b-axis). b Same as (a), taken at T = 138K. The onset of short-range magnetic inhomogenities is apparent in regions with odd numbers of layers. c Real part of the zero-field, AC magnetic susceptibility χ_AC of bulk CrSBr. The data indicate a lack of additional magnetic phase transitions for T > T_N = 132K. d Same as (c) obtained in nonzero bias magnetic fields B_ext. From these data, we extract critical parameters β = 0.22(2) and γ = 2.28(2), both approaching the expected values for an ideal 2D-XY spin model (β = 0.231 and γ = 2.4¹⁴). AC susceptibility data were collected with B parallel to the a-axis with an oscillating field of 1mT.