MAGNETIC-PROPERTIES OF FINE CRYSTALLINE FE-P-C-CU-X ALLOYS

The crystallization process and magnetic properties of Fe-P-C-Cu-Ge-Si amorphous alloys were investigated. After annealing above the crystallization temperature, the bcc Fe particles, with nanoscale grain size, precipitated in the amorphous alloy for a wide P concentration range. The volume ratio of the bcc Fe phase to amorphous was about 30%. The mixed phase of these alloys shows a drastic decrease of coercive force (H(c)) and particle diameter (d) as P concentration increases. The lowest H(c) was obtained for Fe78P16C2Cu0.5Ge3Si0.5, and H(c) and d were 1.8 A/m and 16 nm, respectively. Observation by in situ Lorentz scanning electron microscopy (SEM) revealed that the width of magnetic domains were 0.01 or 0.1 mm and the domain walls with smaller bcc Fe particles moved in a weaker magnetic field than those with larger ones. So the low H(c) is attributed to the decrease of magnetocrystalline anisotropy caused by fine structures. The core loss of fine crystalline Fe-P-C-Cu-Si-Mo alloy, W14/50, was 0.22 W/kg after annealing under a magnetic field of 2.4 kA/m.