Tuning exchange bias in ferromagnetic/ferromagnetic/antiferromagnetic heterostructures [Pt/Co]/NiFe/NiO with in-plane and out-of-plane easy axes

Abstract

In-plane exchange bias (EB) in [Pt/Co]n/NiFe/NiO heterostructures with orthogonal easy axes is investigated. The reversible in-plane EB effect at the ferromagnetic (FM)/FM [Pt/Co]n/NiFe interface allows one to manipulate the value and direction of the EB of the heterostructures, which can be induced by applying a magnetic field larger than the perpendicular anisotropy field of the [Pt/Co]n multilayers. The difference between the EB of the heterostructures after field cooling and zero field cooling disappears at 120 K, which may originate from the exchange coupling at the FM/antiferromagnetic (AFM) NiFe/NiO interface. The NiFe thickness dependence of the bias field of the EB exhibits behavior similar to that in conventional FM/AFM bilayers. The EB can be maintained even at room temperature.