Study of electronic structure in Co/Al₂O₃/Co heterojunctions from first principles

The electronic structure and magnetic properties of Co/Al₂O ₃/Co with O-terminated and Al-terminated interface models of different thicknesses are investigated by first-principles discrete variational method with the local-spin-density approximation. Our calculations results show that the magnetic moment of interface Co layer is enhanced for Al-terminated and weakened for O-terminated interface compared with that of bulk Co. For O-terminated interface models, spin polarization at Fermi energy of Co layer at interface exhibits negative and becomes positive for O layer at interface. In contrast, both Co and Al layers at interface possess negative SP for the Al-terminated interface models. We have also found that TMR ratio of Al-terminated interface models is much larger than that of O-terminated interface. In addition, the change of SP with the thickness of insulating layer is in a similar way as that of magnetic moment.