Effect of pulsed excimer laser irradiation on the magnetic anisotropy of iron-base and nickel-iron-base metallic glasses

Abstract

The present work has examined the effect of pulsed excimer laser irradiation (λ = 308 nm, τ = 26 ns, E = 100 mJ/pulse, N = 1, 5, 10 laser pulses/spot, repetition rate 1 Hz) on the magnetic anisotropy of Fe81B13.5Si3.5C2, Fe78B13Si9, Fe40Ni38Mo4B18, and Fe40Ni40P14B6 metallic glasses. The transmission Mössbauer spectra yielded the intensity ratio R21 of the second to the first line as a function of the number of applied laser pulses. On these grounds, it was found that in the higher magnetostriction samples, controlled changes in the magnetic anisotropy could be induced without onset of bulk crystallization; in the lower magnetostriction samples, a random distribution of the magnetic moment directions was obtained. The conversion electron Mössbauer spectra were characteristic of the amorphous state but showed the same texture as the nonirradiated samples. SEM examinations of the laser-treated surfaces revealed the presence of molten zones subsequently solidified. It is suggested that the correspondingly induced stresses may account for the observed changes in the bulk magnetization orientation, and the model of closure domain structure is supported.