Magnetic and structural properties and crystallization behavior of Si-rich FINEMET materials

The magnetic and structural properties of an Si-rich grade FINEMET alloy with a composition of Fe73.5Si16.1B6.4Nb2.9Cu1.1 in at% [Fe82.7Si9.1B1.4Nb5.4Cu1.4 (wt%)] were investigated after primary and secondary crystallization of ribbon samples. Optimally annealed ribbons exhibited a homogeneous microstructure composed of B7 nm DO3 nanocrystals surrounded by the retained amorphous phase. This is similar to the base FINEMET. Also, a chemical partitioning model, especially of Si, on slowly heated ribbons above the secondary crystallization temperature (B700 C), is presented herein in conjunction with the reaction products and the magnetic transitions. A self-consistent magnetization analysis is presented which for the first time in FINEMET materials correlates a macroscopic approach from the sample magnetization (using experimentally determined microstructural data such as volume fractions of magnetic phases) with an atomistic approach such as nearest-neighbor calculations and the atomic magnetic dipole moments. The estimated magnetic moment exerted by one Fe atom in the as-spun sample is B1.67mB on average, while that in a unit cell of the DO3 phase crystallized from the amorphous is estimated as B1.85mB per Fe atom (B24.2 mB per a unit cell of the DO3 phase). r 2003 Elsevier B.V. All rights reserved.