Magnetostriction and ΔE effect of melt-spun (Fe81−xCoxGa19)80B20 ribbons

Abstract

(Fe81−xCoxGa19)80B20 ribbons, with x = 0, 7, 11, 19, and 23, were made by the single-roller quenching method. The x-ray diffraction patterns showed the A2, D019, and L12 diffraction peaks coexisting with the amorphous matrix background. When Fe was replaced by Co, i.e., when x was increased, the first crystallization temperature (TX1) and Curie temperature (TC1) rose greatly. With a sufficiently heavy load (or weight) stretching the ribbon downward, the magnetization MS was pulled along the vertical direction (i.e., the tension-axis). Then, by applying a horizontal field (HE) up to 6 KOe, we determined the sign and magnitude of the saturation magnetostriction (λS). The Young’s modulus (ES) at magnetization saturation and ΔE effect was estimated from the stress-strain curve. We discovered that the stress-strain curve of (Fe81Ga19)80B20 exhibits the auxetic (or abnormal) characteristic with ΔE < 0. For the rest of the (Fe81−xCoxGa19)80B20 with x ≠ 0, their stress-strain curves are normal with ΔE > 0. Because the sign of λS of the A2 phase is opposite to that of the D019 and L12 phases, λS of (Fe81−xCoxGa19)80B20 is much reduced. However, ΔE/E0 ≒ 36% is quite large for (Fe58Co23Ga19)80B20.