エピタキシャルFe3O4/MgO/Fe(001)三層膜のMgO層を介した層間結合

We report evidence of interlayer exchange coupling (IEC) through a thin MgO layer between Fe3O4 and Fe layers. Both interfaces of Fe3O4 /MgO and MgO /Fe were atomically flat according to RHEED analysis. The IEC of antiferromagnetically favorable interaction was observed in the trilayers with the MgO thickness from 10 to 2 A. The coupling strength J1 became larger with decreasing the MgO thickness, and the maximum value was estimated to be −2.7 erg/cm2 at tMgO=4 A which was comparable with some of the strongest IEC’s for transition-metal spacers such as Ru, Rh for Co and so on. In addition, this J1 was much larger than that observed in Fe/MgO/Fe system, suggesting that the IEC by tunneling mechanism are strongly dependent on electronic structure of magnetic materials.