Fig. 3: Field training exchange bias.

a Illustration of the field training protocol for the setting of temperature and magnetic field as a function of time. Black, red, and blue curves represent the temperature, and the field sweep sequence for positive and negative field training, respectively. The green, red, and blue shades highlight the fieldset, field train, and field sweep regions, respectively. Plots of R_yx hysteresis loops in the magnetic field under zero field initialization at positive (+H_FT) and negative (−H_FT) field training protocols for the different MBT devices of b D2, c D3, d D4, e D5, and f D6. All data were taken at 2 K. The R_yx versus magnetic field curves in all panels are shifted vertically for comparison. The training fields for each curve are labeled in the figures. In c–e, the R_yx curves for positive and negative field training are plotted separately in the left and right panels for clarity. The R_yx hysteresis loops with exchange bias induced by the positive and negative field training are plotted in blue and red curves, respectively. Plots of the exchange bias field (H_EB) and the coercive field (H_C) as a function of the applied training field (H_FT) extracted from the R_yx hysteresis loops of the respective 7SL MBT devices D2–D6 in (g–k), respectively. The shade areas in the H_EB versus H_FT plots highlight the training field regimes with the exchange bias effect.