Effect of Cu, Nb and Ta addition on the structural and magnetic properties of amorphous Fe-Si-B alloys

The effect of successive additions of Cu, Nb and Ta in amorphous Fe77.5Si13.5B9 has been studied using X-ray diffraction and Moessbauer spectroscopy. Addition of Nb/Ta results in an increased near-neighbor distance as well as a decrease in topological order in the system. On the other hand, Cu addition results in a significant increase in the topological order. Addition of Cu does not significantly change the average hyperfine field, whereas, addition of Nb/Ta decreases the hyperfine field. Nb and Ta addition results in appearance of an additional hump in Bhf around 13 T due to Fe atoms with Nb/Ta near neighbors. Thermal annealing of the specimens at 390 deg. C results in changes in the short-range order, which are mainly chemical in nature