GOES’s domain structure in the vicinity and on the lines post-laser treatment

Pulsed laser processing for domain’s refinement is a recent technology implemented on an industrial scale. The present study focuses on the impact of different laser pulse durations on the magnetic properties such as total losses and domain structure of 0.28 mm thick grain-oriented electrical steel (GOES). Three pulse durations are considered Long Pulse (LP), Short-Pulse (SP) and Ultra-Short Pulse (USP). The latter has not been yet applied for domain refinement treatments, hence the interest of this research. Iron loss measured with the single sheet tester (SST) demonstrated a maximum loss reduction of 18 % at induction of 0.5 T and a frequency of 50 Hz following USP laser treatment. At a high induction of 1.7 T for the same frequency, both LP and USP pulse lengths achieved a reduction in total losses of 16 %. Moreover, the behaviour of the magnetic structure under laser treatment was detailed. The magnetic images were visualized by magneto-optical indicator film (MOIF). A reduction from 308 µm to 217 µm in the average domain size was observed post laser treatment with USP duration. Furthermore, the domain structure in the vicinity and on the laser line was investigated on a nanoscale using a magnetic force microscope (MFM). All these results confirmed the dependence of the laser-matter interaction on the laser pulse duration.