The aim of the paper is to study the influence of metalloids content (Si, B), Nb and Cu on the enhancement of soft magnetic properties (ESMP) effect, the 1h optimization annealing temperature Top, the crystallization temperature Tx and the Curie temperature Tc. The following amorphous alloys (melt spinning ribbons) were examined: Fe87Nb2B11, Fe84Nb2B14, Fe76Nb2B22, Fe76Nb2Si13B9, Fe78B22 and Fe75Cu1Nb2Si13B9. As quenched samples were annealed for 1h at temperature Ta (300-900 K) and at room temperature the following measurements were carried out i) magnetic permeability μ (Maxwell-Wien bridge), ii) intensity of magnetic relaxation Δμ/μ, iii) coercive field, iv) magnetization M (magnetic balance) and v) resistivity ρ. The structural changes were examined by making use of X-ray and HRTEM techniques. Both characteristic temperatures Tc and Tx were determined using measurements of M(T) and ρ(T) with heating rate 0.5-10 K/min.
In all cases μ(Ta) show a maximum situated at the temperature Top. For the Fe87Nb2B11, Fe84Nb2B14 alloys (small amount of metalloids) the ESMP effect takes place at temperature range 450-600 K while for the Fe78B22, Fe76Nb2B22, Fe76Nb2Si13B9 alloys (higher amount of metalloids) at 550 - 800 K. An increase of the metalloids content leads to a slowing down of diffusion processes and what follows to an increase of the temperature Top. In all cases the ESMP effect takes place in the relaxed amorphous phase free of αFe or αFe(Si) nanograins. In contrary to this for the Fe75Cu1Nb2Si13B9 alloy the ESMP effect is observed at 600-850 K and is due to formation of nanostructure of αFe(Si).