Fig. 1. EL intensity-voltage and current-voltage characteristics of the devices with Co thickness of 4 nm at 50 K. The device structure is schematically shown in the left inset, and the results fitted according to the power law are shown in the right inset.

Fig. 2. (a) MEL and (b) MC response of the device with the Co thickness of 4 nm under the bias voltage of 25 V at 50 K is plotted. Red solid lines show the non-Lorentzian line shape.

Fig. 3. MEL and MC values as a function of bias voltage in the device under the applied field of 42 mT at 50 K.

Fig. 4. Temperature dependence of MEL in the device with the Co thickness of 4 nm under 25 V.

Fig. 5. MEL and turn-on voltage as a function of Co thickness in the devices under the applied field of 42 mT at 50 K.

Fig. 6. Normalized hysteresis loops for the samples with different Co thicknesses.