Figure 3: Magnetic anisotropy reversal at the quantum limit.

The angle dependence of the non-oscillatory torque background at three different field levels: (a) In the high-field regime at 60 T above the quantum limit (QL) for most angles, (b) at 30 T in an intermediate regime, and (c) at 10 T below the QL. The torque in the low- and high-field regions both follow a sin(2θ) dependence, yet of opposite sign. This change in the magnetic anisotropy is most evident in the intermediate field region, where the system crosses the quantum limit as a function of angle. At low angles, the system follows the high-field anisotropy, then suddenly transitions into the low-field anisotropy at high angles where the quantum limit exceeds 30 T, leading to pronounced deviations from the usual sin(2θ) behaviour. Small deviations from the sign reversal between the 10 T and 60 T torque may appear due to the eventual cross-over into the low-field regime even at 60 T at high angles, and the field dependence of the susceptibility.