Optimising Magnetic Flux Concentration with CoZrNb​ and FeSiBNbCu Thin Films: Effects of Annealing on Magnetic Properties

Magnetic flux concentration (MFC) materials are crucial for amplifying magnetic fields, thereby enhancing local magnetic flux density. In this study, we develop MFCs using CoZrNb (CZN) and FeSiBNbCu (Finemet). Films with thicknesses 100-1200 nm were deposited by magnetron sputtering and annealed at various temperatures. Magnetic properties—saturation magnetisation (Ms), coercivity (Hc), anisotropy field (Hk), and permeability (µ)—were evaluated using a vibrating sample magnetometer (VSM). CZN showed stable Ms across all temperatures, but with increases in Hc and Hk and a decrease in µ, suggesting optimal soft properties in the as-deposited state. In contrast, annealing improved Finemet's performance, featuring enhanced Hc and Hk between 200°C and 550°C, along with a peak in µ around 500-550°C. Thus, CZN is suited for applications where annealing is impractical, as its properties are optimised without further processing. Finemet, however, requires annealing to unlock its full potential, making it suitable for applications that can tolerate higher temperatures. Both materials are promising for magnetic sensor integration, though the optimal choice depends on whether the devices can withstand annealing during fabrication. This research was supported by the National Institute of Biomedical Imaging and Bioengineering (NIBIB) of the National Institutes of Health under Award Number UG3EB034695. The content presented here reflects the views of the authors and not necessarily those of the NIH.