Effects of femtosecond laser ablation on Vitrovac 6025X

In the development of extremely sensitive magnetic sensors, the processing of the soft magnetic materials is extremely critical as this affects the performance of the materials in the sensing element. Laser cutting is a fast, direct and simple approach to process soft magnetic materials into magnetic sensors. Traditionally, nanosecond laser introduces thermal stresses which greatly deteriorate magnetic properties. Femtosecond laser, which has a lower ablation threshold and smaller heat affected zones, stands to be a potential candidate to solve such thermal and processing issues of processed magnetic materials. In this paper, Ti: sapphire femtosecond laser was used to pattern and cut commercially available magnetic ribbon (Vitrovac 6025X) into a square of 5 mm × 5 mm with a 2 mm long channel at the centre of the specimens. Laser fluence was varied to investigate the effects of femtosecond laser on (i) quality of laser ablated channel; (ii) material composition; and (iii) magnetic properties of the magnetic ribbon. Channels with well-defined edges were observed at lower laser fluences. With increasing laser fluence, molten walls were formed. Chemical composition of the magnetic ribbon remains similar at the channel walls, regions just beside the walls and no laser-processed areas. Hysteresis loops obtained for varying laser fluences and varying the number of ablated channels in the magnetic foil suggest that femtosecond laser processing does not significantly affect the coercivities and magnetic anisotropies of the workpiece material.