Temperature dependence of creep induced anisotropy in nanocrystalline Fe-Cu-Nb-Si-B alloys

Abstract

Nanocrystallisation of Fe₇₅Cu₁Nb₃Si₈B₁₃ under tensile stress results in a creep induced anisotropy which, at room temperature, is characterised by a magnetic easy axis along the stress axis. However, this magnetic easy ribbon axis becomes a magnetic hard ribbon axis when the measuring temperature T decreases below a compensation temperature T ₀ where the creep induced magnetic anisotropy vanishes. Accordingly, the magnetisation curve changes from a square loop for T > T ₀ to a linear loop with low remanence forT < T ₀. In the present case (8 at% Si), T ₀ is about −2 °C for the fully developed nanocrystalline state. Although slightly depending on the annealing conditions, T ₀ is primarily determined by the Si content and shifts towards higher temperatures by about 50 °C per at% Si with increasing Si concentration.