Surface mediated impact of thermal treatment ambience on magnetic properties of Fe-Nb-Cu-B-Si nanocrystalline ribbons

The less silicon, the more pronounced is the diversity between surfaces and ribbon interior of non-vacuum annealed Fe-Nb-Cu-B-Si nanocrystalline Finemets. The diversity significantly impacts material's magnetic properties particularly by engaging surface-created macroscopic forces in magnetoelastic interaction. A medium-Si Finemet (10 at%) was investigated using several surface analysis methods and compared to standard Si-rich Finemet. Oxides were detected on the surfaces after non-vacuum annealing. No explicit contiguous oxide layer was revealed. Surface crystallization is considered to be the direct source of the macroscopic forces.