Observation and characterisation of magnetisation ripple using Lorentz transmission electron microscopy

The dramatic effect of seed layer addition resulted in grain size and texture reduction, an increase in uniaxial anisotropy and a reduction in magnetisation ripple properties. This suggests that the film is a good candidate for controlling properties of Ni45Fe55 thin films, whilst maintaining a high magnetic moment density.<br><br>Micromagnetic modelling of magnetisation ripple using MuMax3 software has been presented using two different methods.

Both models produced visually representative simulated Fresnel images, with work specifically focusing on magnetisation reversal processes and the quantitative analysis of magnetisation ripple properties. Models produced insights into the effect of parameters such as grain size, inter-granular exchange and magnetocrystalline anisotropy directionality.<br><br>Lastly, we can quantitatively assess the physical and magnetic variations between permalloy magnetostrictive samples with varying signs, without the need for external straining, to represent normal operating conditions in HDD devices.

Analysis revealed near identical physical properties, with a subtle variation in bulk and magnetic ripple properties. However, it is not possible to determine if these variations are exclusively due to differences in magnetostrictive properties or if it is more likely due to compositional variations.