Fig. 4.
Angular dependent Hall effect measurements and modified Stoner–Wohlfarth model. a, b Rxy(B) loops at different angles between the applied magnetic field and the direction perpendicular to the surface of the nanoflake with a thickness of 10.4 nm. At 0°, the surface of the nanoflake is perpendicular to the magnetic field. c Normalized Rxy(B) curve at 2 K measured at 85° from 6 to −6 T. The fitting curve is based on the Stoner–Wohlfarth model. d The effective angular dependence of effective coercivities at different temperatures. The solid curves are the fitting curves based on a modified Stoner–Wohlfarth model. From b we can tell that the remanences of the Rxy loops at angles >85° show pronounced decreases and a divergent coercivity value was obtained at 90°, an angle beyond the range included by the modified Stoner–Wohlfarth model. Based on this experimental result, the theoretical fittings were only performed to 85°. e The temperature dependence of KA and V. KA was fitted by the Stoner–Wohlfarth model, while V was fitted based on the fitted KA and the modified Stoner–Wohlfarth model (Supplementary Note 4). f Illustration of the variables used in the Stoner–Wohlfarth model. The dashed line is the easy axis of the magnetic anisotropy in FGT nanoflakes. g Schematic diagram of a magnetic system changing from a metastable to an unstable state