Abstract
Two different laser sources, namely the CO₂ laser and continuous-wave thulium-doped fibre laser were individually used to study their effects on the resulting changes in magnetic domains structure, coercivity, and nanohardness of Fe-3.2Si grain-oriented electrical steel sheets. The CO₂ laser with a constant power of 30 W, constant frequency of 1 kHz and variable scribing speed in the range of 10–50 mm s^–1 was used to perform the first series of five different laser scribing treatments. Separately, the second series of next five laser scribing treatments was performed using thulium-doped fibre laser operating at a constant scribing speed of 2.4 mm s^–1 and variable laser power in the range of 2–10 W. The results showed that compared to the laser untreated material with a coercivity of 0.21 A m^–1, distinguishable improvements in soft magnetic characteristics (i.e., coercivity reduction) were obtained after the all laser treatments used. At the same time, lowered nanohardness values were indicated in central parts of laser scribed areas. The major effects responsible for the observed coercivity improvements are related to optimal refinement of magnetic domains structures by applied laser treatments.

Key words
CO₂ laser, thulium-doped fibre laser, electrical steel, laser scribing, magnetic domains, coercivity

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