Magnetostrictive Properties of Finely Crystallized (Tb, Dy)-Fe-B Alloys

The magnetostrictive properties of (Tb, Dy)-Fe-B alloys with fine (Tb, Dy)Fe2 grains crystallized from an amorphous state were studied.Amorphous phases were obtained for rapidly quenched ((Tb1−xDyx)0.33Fe0.67)100−yBy alloys with B content over 5 mol%.Increasing of Dy content makes the alloys easy to be crystallized during rapidly quenching process, and then it is necessary to increase the B content for achieving an amorphous state.Annealing of amorphous alloys gives a finely crystallized grains of RFe2 compound with the size of around 10 nm, which yields the high magnetostrictive susceptibility and low coercive force.Maximum magnetostrictive susceptibility, (dλ/dH)H=0.1=55.8×10−10(m/A), of ((Tb1−xDyx)0.33Fe0.67)100−yBy alloys was obtained in x=0.3 and y=6. This alloy exhibited the giant magnetostriction, λH=1.28=722×10−6 at the applied magnetic field of 1.28 MA/m.