Effect of rare earth additions on magnetic properties of Fe82Nb2B14RE2 (RE = Y, Gd, Tb and Dy) amorphous alloys

In the present paper the influence of RE alloying additions (Y, Gd, Tb and Dy) on magnetic properties (Curie temperatures, low temperature magnetization, zero field cooling–field cooling curves, domain structure, room temperature magnetostriction and magnetic permeability) of amorphous alloys of type Fe82Nb2B14RE2 are carefully examined. It was shown that substituting of yttrium atoms by magnetic elements, i.e. Gd, Tb and Dy leads to (i) an increase of the Curie temperature of amorphous phase from 416 K (for Fe82Nb2B14Y2) to 450 K (for Fe82Nb2B14Gd2) and (ii) a decrease of magnetization in saturation (magnetic field 7 T) which can be explained by antiferromagnetic Fe–RE coupling resulting in a decrease of magnetic moment calculated per magnetic atom from 2.00 μB for the Fe82Nb2B14Y2 alloy (Fe in amorphous phase) to 1.51 μB for the Fe82Nb2B14Tb2 alloy. It was concluded that Tb and Dy alloying additions introduce a local magnetic anisotropy responsible for significant decrease of initial magnetic permeability (about 5 times in relation to Fe82Nb2B14Y2 or Fe82Nb2B14Gd2 alloy), increase of magnetic irreversibility effect measured at 2 K (about 10 times in relation to the same alloys) and appearing of the finger-print magnetic domain regions (not observed for the Fe82Nb2B14Y2 and Fe82Nb2B14Gd2 alloys).