The low‐field magnetic properties of Fe80B20glass are examined. Measurements are reported for straight strips, stressed and unstressed, for as‐cast/as‐wound toroids and for field‐annealed toroids. Due to the positive magnetostriction (lgr;s=31×10−6) of the alloy, the low‐field magnetic properties of strips are improved by applied tensile stress. Similarly, toroids annealed to remove compressive stresses induced by winding (cooled in a magnetic field) are superior to unannealed toroids. Field‐annealed Fe80B20toroids show a coercivity of ∼0.04 Oe, a permeability of 4000 at 20 G, and a remanence ratio of 0.77Bs(Bs=16 kG). The approach of the magnetization to saturation for field‐annealed toroids indicates a magnetic anisotropy energy density of about 5×103erg/cm3. This low magnetic anisotropy, as well as the low coercivity and high resistivity (145 mgr;OHgr; cm±10) exhibited by Fe80B20lead to low core loss under ac excitation, i.e., 0.10 W/kg (measured at 1 kHz and a maximum induction of 1 kG on a field‐annealed toroid).
展开▼
