Stray field effects on the magnetic response of a spin-torque vortex oscillator

Details

Supervisors

Abreu Araujo, Flavio

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil électricien, à finalité spécialisée

Abstract

The objective of this Master thesis is to study the magnetic properties of spin-torque vortex oscillators (STVOs), which are integral components in spintronic-based neuromorphic architectures for artificial intelligence hardware systems. STVOs, which function as artificial neurons due to their non-linear input-output characteristics, are magnetic tunnel junctions (MTJs) with free-layer magnetization in a vortex state. The research is focused on the effects of stray fields, specifically the synthetic antiferromagnet (SAF) field and the Ampère-Oersted field (AOF) generated by an out-of-plane current, on the magnetization of the free layer. The layer in question exhibits bistability, manifesting in two distinct states in the absence of an external field. The study demonstrates, through the use of micromagnetic simulations in MuMax3, that the SAF field has a significant impact on the hysteresis loop and magnetic state transitions. Although the AOF has a relatively minor impact, it still influences critical magnetic events such as vortex annihilation and nucleation, with a linear relationship observed between the field difference and current amplitude. These findings contribute to a deeper understanding of the role of stray fields in the magnetic behavior of STVOs and establish a foundation for further investigation in this emerging area.