The effect of oscillatory interlayer exchange coupling on current-induced magnetization switching in pentalayer nanopillar alloys

The oscillatory interlayer exchange coupling (OXC) between ferromagnetic layers sandwiched by non-magnetic spacer layers plays a significant role in spintronic device function. In this work, the effect of OXC on the current-induced magnetization switching process in four different pentalayer nanopillar alloys is numerically investigated by solving the dynamical equation governed by the Landau–Lifshitz–Gilbert–Slonczewski (LLGS) equation. The four nanopillars consist of four ferromagnetic alloys, CoPt, CoFeB, Fe(₈₅)B(₁₃)Ni(_2) and EuO, which serve as pinned layers and free layers, with copper forming a spacer layer between all the layers. The critical current density required to switch the magnetization of the free layer is computed for all the devices and the values are (mathsf {}{0.6} imes 10 ¹¹{ ext {Am}}^-2), (1.31 imes 10 ¹¹ { ext {Am}}^-2), (2.24 imes 10 ¹¹ { ext {Am}}^-2), (3.27 imes 10 ¹¹ { ext {Am}}^-2) for CoPt, CoFeB, ({ ext {Fe}}₈₅{ ext {B}}₁₃{ ext {Ni}}_2) and EuO device, respectively. Then we studied how the thickness of the Cu layer influences the OXC field. Furthermore, we investigated the effect of Cu layer thickness on critical current density and magnetization switching time for all the four devices by numerically solving the LLGS equation and they exhibit oscillating behaviour. We can reduce the critical current density and switching time substantially by controlling the OXC field acting on the free layer and choosing the magnetic material having low saturation magnetization as the free layer. The OXC field is optimised by fixing the Cu spacer thickness from 1.7 to 1.9 nm in the pentalayer nanopillar device.