Equilibrium surface magnetization of α-Cr₂O₃ studied through interfacial chromium magnetization in Co/α-Cr₂O₃ layered structures

We show experimental evidence of the equilibrium surface magnetization of α-Cr₂O₃(0001) by studying chromium magnetization at the Co(111)/ α-Cr₂O₃(0001) interface. The soft X-ray magnetic circular dichroism intensity from uncompensated Cr spins was found to be almost independent of the interface roughness and exchange anisotropy energy. Moreover, no exchange bias training effect was found, except in the transition temperature regime, suggesting that the antiferromagnetic spin structure, including the interface spin arrangement, is in equilibrium. Furthermore, the exchange bias polarity was switched by magnetoelectric field cooling, which is also a salient feature of the surface magnetization of α-Cr₂O₃(0001).