Exchange Bias Effect and Ferromagnetic Resonance Study of NiO/NiFe/NiO Trilayers with Different Thicknesses of NiO Layers

Abstract

Antiferromagnetic (AFM1)-ferromagnetic (FM)-antiferromagnetic (AFM2) multilayer films are fabricated using a magnetron sputtering technique. The AFM1, FM, and AFM2 layers are NiO, NiFe, and NiO films, respectively, where AFM1 and AFM2 are of the same thickness ranging from 10 to 60 nm. The exchange bias effect and ferromagnetic resonance of NiO/NiFe (50 nm)/NiO have been investigated using the vibrating sample magnetometer (VSM) and ferromagnetic resonance (FMR) meter. Both saturation magnetization (M s) and coercivity (H c) increase first and then decrease with the increasing thickness of NiO layers. The maximum values (M s = 457 kA/m, H c = 1.86 kA/m) are achieved when the NiO thickness is 30 nm. The in-plane resonance field (H r∥) and ferromagnetic resonance linewidth (ΔH ∥) show the lowest values (H r = 77.4 kA/m, ΔH ∥ = 7.2 kA/m) which occur when the thickness of NiO layers is 30 nm. The dependence between exchange bias and NiO film thickness in NiO/NiFe/NiO trilayers has also been discussed.