Magnetic properties of Fe-based bulk ferromagnetic glasses

Abstract

Several Fe-based ferromagnetic bulk amorphous alloys, having compositions Fe 61Co 10Zr 5W 4B 20; Fe 61Co 10Zr 5W 2Nb 2B 20; Fe 61Co 10Zr 2.5Hf 2.5W 2Nb 2B 20, have been prepared by suction casting, in the form of 1 mm diameter rods, and by melt spinning in the form of thick ribbons (thickness ∼200 μm). All these glasses have a large supercooled region T x – T g, ranging from 51 to 70 K, consistent with a large glass forming ability, that is promoted by the substantial differences in the atomic sizes of the constituent elements. We have obtained a saturation polarisation (μ 0M S) of ∼0.8 T for Fe 61Co 10Zr 5W 4B 20 and 0.9 T for Fe 61Co 10Zr 5W 2Nb 2B 20 and Fe 61Co 10Zr 2.5Hf 2.5W 2Nb 2B 20, for both rod and ribbon forms. The coercivities of the samples range from 25 to 50 A/m, for ribbon and from 100 to 300 A/m for rods, when measured at 5 Hz. The coercivity is a parameter that is very sensitive to magnetic inhomogeneity and the data indicate some degree of such inhomogeneity in the samples, especially for the rods. Magnetoelastic resonance experiments were also performed, giving values of Young modulus of about 160 GPa, and magnetostriction coefficients of about 10 −5.