Influence of thickness on magnetic properties of RF-sputtered amorphous CoNbZr thin films

TL;DR

This study investigates how the magnetic properties of RF-sputtered amorphous CoNbZr thin films vary with thickness, revealing significant changes in coercivity, permeability, and domain structure as thickness increases from 52 nm to 1040 nm.

Contribution

It provides a detailed analysis of the relationship between film thickness and magnetic properties, highlighting the transition in domain wall types and domain structures in amorphous CoNbZr films.

Findings

Magnetic properties decrease with increasing thickness.

Domain structures evolve from irregular to flux-closure as thickness increases.

Transition between Néel and Bloch domain walls occurs around 84 nm.

Abstract

Amorphous sputtered Co-based thin films are widely used as soft magnetic materials in applications such as sensors, inductors and magnetic flux concentrators. The magnetic properties of these films can be controlled by deposition parameters like film thickness, argon pressure, deposition rate and others. In this study, we present a detailed investigation of the magnetic properties of RF-sputtered Co$_{91}$Nb$_7$Zr$_2$ films with thicknesses ranging from 52 nm to 1040 nm. These amorphous films exhibit an average saturation magnetisation of 1.01(4) MA/m. As the film thickness increases, there is a significant decrease in coercivity, remanent-to-saturation magnetisation ratio M$_r$/M$_s$, and maximum permeability. The change in macroscopic magnetic properties is also reflected by the domain structure. At a thickness of 52 nm, the remanent domain state shows irregular domains, while films thicknesses above 208 nm exhibit flux-closure domain structures instead. The thickness-dependent modifications are attributed to the transition between N\'eel and Bloch type domain walls, which is expected to occur at approximately 84 nm.