Soft magnetic properties of metallic glasses—recent developments

Abstract

Two major aspects of the soft magnetic properties of metallic glasses, i.e., high magnetic permeability and high saturation induction, are discussed. Recent development in the area of high permeability materials is centered around the zero‐magnetostriction Co‐rich metallic glasses having Si and B as metalloids. The heat treated materials studied thus far show low‐field magnetic properties comparable or superior to those of commercial supermalloy. A typical example includes an effective permeability at l kHz exceeding 50,000. Attractive high saturation induction metallic glasses are found in the series Fe₈₂B_18−xSi_x. Typical dc results for field‐annealed samples of this glass with x=8 are H_c=0.03 Oe, B_r=12 kG and μ (20) =8,000. Core loss under sine flux conditions at 60 Hz is 0.24 watts/kg at 16 kG. This value is nearly five times lower than that of the widely used power transformer material grade M‐4 Si/Fe (1.3 watts/kg) and well below that of Fe‐B glass. The stability against crystallization of Fe₈₂B₁₀Si₈ is higher than that of Fe₈₀B₂₀.