SOFT MAGNETIC-PROPERTIES OF CARBIDE-DISPERSED NANOCRYSTALLINE FILMS WITH HIGH THERMAL-STABILITY

Nanocrystalline Fe-M-C, Co-M-C, and Ni-M-C (M = group IVa-VIa metals) films in which extremely fine M-carbide particles are dispersed were prepared by annealing sputter-deposited amorphous alloy films. Of these films, the Fe-M-C and Co-M-C films exhibited good soft magnetic properties. These soft magnetic properties were maintained after annealing at elevated temperatures, because carbide particles dispersed in the films considerably retard the grain growth of Fe-rich or Co-rich nanocrystallites. Films containing Ta or Hf exhibit particularly high thermal stability (around 1000 K). On the other hand, Zr and Hf are suitable for obtaining high saturation magnetization, I(s), because the amount of these elements needed for amorphization is less than other M elements. The highest I(s) of films containing Zr or Hf was 1.7 T for Fe-M-C and 1.6 T for Co-M-C films. Because the magnetostriction of Fe-M-C films is dominated primarily by the C concentration dissolved into Fe, zero-magnetostrictive films can easily be attained by controlling the C to M ratio or annealing conditions. In addition to the good performance of Fe-Hf-C films, a higher I(s) value of 2.0 T was achieved by multilayering the Fe-Hf-C with Fe, and improved frequency characteristics of permeability as well as higher thermal stability by about 100 K was achieved by Si additions without sacrificing other properties. These carbide-dispersed nanocrystalline films are suitable for use in high-density magnetic recording heads fabricated by glass bonding processes.