The effect of furnace annealing and surface crystallization on the anisotropy, ΔE and magnetoimpedance effects in Fe71Cr7Si9B13 amorphous wires

Abstract

The dependence of the magnetization loops, coercivity, anisotropy constant, ΔE and magnetoimpedance (MI) effects in positively magnetostrictive Fe71Cr7Si9B13 amorphous wires on annealing conditions were studied. Samples were annealed at temperatures of 440°C and 460°C for durations between 0.3 and 300 min. The results indicate that progressive annealing first leads to relief of internal stresses and annealing of wires at 460°C for 60 min produces the minimum coercivity of about 1 A m−1. Further annealing increases the coercivity and anisotropy, due to partial crystallization at the surface. It was found that the anisotropy changes its direction to the circumferential direction with the surface crystallization. The maximum change in Young's modulus was measured to be about 75% in a partly surface crystalline sample. It was observed that the magnitude of the MI effect of the stress relieved sample could exceed 200% at 1 MHz.