Interlayer exchange coupling and its temperature dependence in [Pt/Co]4/MgO/[Co/Pt]2 perpendicular magnetic tunnel junctions

In the [ Pt / Co ] 4 / MgO / [ Co / Pt ] 2 perpendicular magnetic tunnel junctions, we have observed antiferromagnetic interlayer coupling when the spacer thickness is larger than 12 A, and a transition to ferromagnetic coupling for lower MgO thickness. The dependence of the interlayer coupling strength on the MgO spacer thickness is well fitted by the theory of free-electron model, providing an unambiguous experimental proof for interlayer exchange coupling theory. The thermal behavior of interlayer coupling shows a translation from antiferromagnetic to ferromagnetic coupling at 145 K. It can be mainly ascribed to the temperature-dependent enhancement of the magnetization of the ferromagnetic layers.