Magneto-optical microscopy as a favourite tool to probe focused ion beam patterning at low dose

Checking the effect of focused Ga ion beam (FIB) irradiation on a target at very low dose is still a challenge. High-resolution magneto-optical microscopy and scanning electron microscopy (SEM) are used to investigate weakly irradiated tracks patterned by FIB on a Pt/Co(1 nm)/Pt ultrathin ferromagnetic film. The two techniques give complementary results on surface film morphology and magnetism. Magneto-optical microscopy, linked to tiny ion rearrangements at interfaces, is found to be more sensitive than SEM to detect damages after irradiation at very low dose.