Magnetostriction of rapidly quenched Sm-Fe-B alloys

The magnetic and magnetostrictive properties of melt-spun ribbons of (Sm_0.33Fe_0.67)_1-xB_x (where x=0, 0.01, 0.02, 0.03 and 0.04) alloys are investigated as a function of wheel speed during melt-quenching using a single-roll technique. Contrary to the previous results on Dy-Fe and Tb-Fe based systems, the magnetostrictive characteristics seem to vary in a rather unexpected way, although the grain size decreases with wheel speed and an amorphous phase is formed at high wheel speeds and/or at high B contents, as expected. This is mainly because, for the alloys with x≤0.02, the absolute value of magnetostriction is exceptionally large for the ribbons fabricated at the wheel speed of 10 m s^-1 (and also 20 m s^-1 for the B-free alloy). The magnitude of magnetostriction of the present melt-spun Sm-Fe-B alloy ribbons is found to be small and also the sensitivity of magnetostriction is poor at low magnetic fields except for high wheel speeds and high B contents. The coercive force is observed to be well matched with the sensitivity of magnetostriction at low fields; good (poor) sensitivity is attained at low (high) H_c. Saturation magnetization does not vary with B content and is 66.2 emug^-1 (at x=0.04 and 50 m s^-1).