Microstructure and magnetic properties of FeCoZr(Mo)BGe nanocrystalline alloys

The microstructure and magnetic properties of Fe₄₀Co₄₀Zr₉B₁₀Ge₁ (Mo-free) and Fe₄₀Co₄₀Zr₅Mo₄B₁₀Ge₁ (Mo-containing) nanocrystalline alloys, prepared using an amorphous crystallization method, were investigated. Mo addition affects the crystallization of the Fe₄₀Co₄₀Zr₉B₁₀Ge₁ amorphous alloy and decreases the grain size of the α-Fe(Co) phase below 650 °C. For the Mo-free alloy annealed at 600 °C and the Mo-containing alloy annealed at 575 °C, with a single α-Fe(Co) crystallization phase and approximately similar crystallization volume fractions, the Mo-containing alloy showed smaller, more regularly shaped grains and a significantly narrower grain-size distribution than the Mo-free alloy. The Fe and Co contents in the nanograins of the two alloys also differed. For the Mo-free alloy, a higher concentration of Co distributed in the residual amorphous matrix. For the Mo-containing alloy, a higher concentration Co dissolved in the nanograins. The specific saturation magnetization and coercivity of the Mo-free alloy were 1.05- and 1.59-times higher than those of the Mo-containing alloy, respectively.