Magnetic Properties and Microstructures of Nanocrystalline Fe-M (M=Y,Ce)-O Films

Recently, Fe-based nanocrystalline soft magnetic alloys with a high saturation magnetization B_s, produced by melt-spinning and sputtering, have been discovered. Most of these alloys are obtained by annealing an amorphous phase, and consequently there is a limit to the B_s imposed by glass-forming materials. We have been studying soft magnetic alloy films with high B_s, which have nanocrystalline structures in the as-deposited state. In this paper, we describe the magnetic and structural properties of nanocrystalline Fe-M-O (M=Y,Ce) alloy films. The Y or Ce and O elements in the films tend to make the bcc grains finer in the as-deposited state, and also repress the growth of grains during annealing through the presence of very fine (less than 10 nm in size) oxide particles containing Y or Ce. The highest B_s and μ_e values at 1 MHz, and the lowest H_c value, were 1.95 T, 1200 and 0.6 Oe respectively for a Fe₈₅Y₄O₁₁ film annealed at 773K for one hour.