Study of Spin-Orbit Interactions and Interlayer Ferromagnetic Coupling in Co/Pt/Co Trilayers in Wide Range of Heavy Metal Thickness

TL;DR

This study investigates how varying the thickness of platinum in Co/Pt/Co trilayers affects spin-orbit interactions, magnetic properties, and interlayer coupling, combining experimental measurements with theoretical modeling.

Contribution

It provides new insights into the dependence of magnetic and spin-orbit properties on Pt thickness in multilayer structures, supported by comprehensive experimental and simulation analyses.

Findings

Pt thickness influences magnetic anisotropy and magnetoresistance.

Interlayer ferromagnetic coupling can be tuned via Pt thickness.

Spin-orbit torque fields vary with Pt layer thickness.

Abstract

The spin-orbit torque, a torque induced by a charge current flowing through the heavy-metal conducting layer with strong spin-orbit interactions, provides an efficient way to control the magnetization direction in heavy-metal/ferromagnet nanostructures, required for applications in the emergent magnetic technologies like random access memories, high-frequency nano oscillators, or bio-inspired neuromorphic computations. We study the interface properties, magnetization dynamics, magnetostatic features and spin-orbit interactions within the multilayer system Ti(2)/Co(1)/Pt(0-4)/Co(1)/MgO(2)/Ti(2) (thicknesses in nanometers) patterned by optical lithography on micrometer-sized bars. In the investigated devices, Pt is used as a source of the spin current and as a non-magnetic spacer with variable thickness, which enables the magnitude of the interlayer ferromagnetic exchange coupling to be effectively tuned. We also find the Pt thickness-dependent changes in magnetic anisotropies, magnetoresistance, effective Hall angle and, eventually, spin-orbit torque fields at interfaces. The experimental findings are supported by the relevant interface structure-related simulations, micromagnetic, macrospin, as well as the spin drift-diffusion models. Finally, the contribution of the spin-orbital Edelstein-Rashba interfacial fields is also briefly discussed in the analysis.