Midway Evaluation in Physics - Ásgeir Tryggvason

Student:
Ásgeir Tryggvason

Title of thesis:
Magnetization dynamics and spin transport in amorphous magnetic films and heterostructures

Doctoral committee:
Dr. Friðrik Magnus, research professor at the Science Institute Dr. Snorri Þorgeir Ingvarsson, professor at the Faculty of Physical Sciences
Dr. Unnar Bjarni Arnalds, professor at the Faculty of Physical Sciences

Ágrip á ensku:
Amorphous magnetic thin films are of interest for spintronic devices but much is still unknown about their spin transport properties and performance at high frequencies. We study the dynamic magnetic properties of CoAlZr thin films, in particular the Gilbert damping, and the influence of magnetic proximity effects and Curie temperature on damping. A key innovation in this work is the introduction of a novel control parameter for heterostructure design: films with continuously modulated composition. We achieve films with both a linear gradient and a sinusoidal variation in composition in the growth direction, and analyse the density variations with XRR and PNR measurements. In a separate study, we examine interlayer exchange coupling in amorphous trilayer structures, using ferromagnetic resonance measurements. We compare two types of spacer layers: paramagnetic AlZr and a paramagnetic composition of CoAlZr, the latter known to exhibit proximity-induced magnetization. We evaluate interlayer exchange coupling and find that strong coupling is associated with the presence of proximity-induced magnetization in the CoAlZr spacer layers. We are also working on evaluating spin transport parameters, such as spin diffusion and spin mixing conductance which are critical for understanding and optimizing spintronic devices. By correlating these transport properties with the structural and magnetic characteristics of the films, we aim to establish a comprehensive understanding of spin dynamics in amorphous systems. Finally, we introduce preliminary results in a study of spin-orbit torque induced switching in amorphous trilayers.