Magnetically soft nanomaterials for high-temperature applications

FeCo-based soft magnetic alloys of compositions Fe₄₅Co₄₃Cu₁B_3.6Zr_7.4-xAM_x, where x=3.7 at.% and 7.4 at.%, and the alloying metals (AM) are Nb and Hf and were prepared in the form of amorphous ribbons by a melt-spinning technique. A two-phase microstructure, consisting of α-FeCo nanocrystals and amorphous matrix, was created by partial devitrification of the amorphous alloys during annealing for 1 h at temperatures 500°C-600°C. The crystallization process of the amorphous alloys was studied using differential scanning calorimetry, X-ray diffractometry, and transmission electron microscopy. The quasi-static hysteresis loop was measured using an inductive method. Partial replacement of zirconium by hafnium improved thermal stability of the amorphous structure and the magnetic properties of the alloys studied. The effect of niobium is opposite. The best magnetic properties were found in the alloy Fe₄₅Co₄₃Cu₁B_3.6Zr_3.7Hf_3.7. It was found that the nanocrystallization temperature strongly influences the thermal stability of the magnetic properties of the alloys studied.