Structure and Magnetic Properties of FeRuGaSi Multilayer Thin Films

The structure and magnetic properties of FeRuGaSi in thin films (e.g. Fe sub 72.3 Ru sub 7.3 Ga sub 5.8 Si sub 14.5 ) used in very-high-frequency (150 MHz) recording head has been studied. The best soft magnetic properties, coercivity of 0.2-0.3 Oe, permeability of 2000 at 1 MHz and 400-500 at 150 MHz, and magnetostriction of < 10 exp --6 , were obtained after annealing at 450-500 deg C. This magnetic behavior was attributed to the phase transformations and the increase in the grain size of the films occurring during the annealing process. Transmission electron diffraction revealed that B2 and/or DO sub 3 ordered phases were formed in the films depending on the annealing temperature. However, good soft magnetic properties were associated with the formation of the B2 phase with low crystal anisotropy and saturation magnetostriction. These results are somewhat in contrast to what has been observed in Sendust, where magnetic softness is usually attributed to the formation of the DO sub 3 phase.