Fig. 2. Spontaneous exchange bias.

$R_{\mathrm{xy}}$ as a function of applied magnetic field for different low values of cooling fields at 2 K. For each field, both a positive sweep protocol (PSP) and a negative sweep protocol (NSP) were performed, where the sample is warmed up to 250 K—well above $T_C=175$ K—between the two to negate the SEB magnetization effect. The initial field sweeps for the zero-field cooled curve are marked with arrows, but are clear inside the hysteresis loop area for all fields. These indicate that the initial magnetic state is unsaturated, and that the SEB is indeed induced at the low temperature, by the specifics of the field sweep protocol. The curves for different cooling fields are shifted vertically for clarity and an easier comparison.