Correlation between structure and magnetic properties of “finemet” type microwires
Effect of geometrical parameters (metallic core diameter, glass cover thickness) on the structure and magnetic properties of glass-coated Fe-Si-B-Nb-Cu microwires is investigated. The structure of as-prepared Fe73.8Cu1Nb3.1Si13B9.1 microwire is nanocrystalline, consisting of α-Fe(Si) crystallites in a residual amorphous matrix. It is shown that great residual stresses arising at the manufacturing processes greatly influence the microstresses and crystallite sizes of α-Fe(Si) crystals. An increasing of stress magnitude results to structure refinement. The size of α-Fe(Si) crystals and crystallized volume fraction decrease from approximately 105 nm and 71 % to 9 nm and 34 %, respectively, with glass cover thickness increasing. Grain size refinement of α-Fe(Si) leads to the considerable decrease of coercivity of microwires from 1800 A/m to 160 A/m.