Giant magnetostriction in rapidly solidified Fe-Pd ribbon

Ferromagnetic shape memory alloy (FSMA) is recently known as a new type of magnetically driven solid state actuator material, which has large strain as well as a quick response to the mechanism of re-arrangement of martensite twin by magnetic field. In this study, Fe-29.6 at%Pd alloy ribbons formed by rapidly solidified, melt-spinning methods were studied. Samples showed strong anisotropy and large magnetostriction, epsilon = 600 similar to 800 x 10(-6) at nearly perpendicular direction to its plate surface (theta = 90 degrees) at room temperature. The epsilon vs. temperature, T curve had a maximum at 370 similar to 400 K, then decreased steeply with increasing T, Magnetization, M and applied magnetic field, H loops also showed anisotropic behavior similar to epsilon vs, H curve. It was found that the coercive force, H-c = 6.1 kA . m(-1), at theta = 90 degrees decreased steeply in the range of 293 to 320 K and then it reached to constant, 2 kA . m(-1) with T. Since the remarkably decrease of Hc is caused by the disappearance of the obstacles against magnetization, ie, martensite twin variants in the lower temperature phase, it is suggested that A(t) equals to about 320 K. By X-ray diffraction analysis, the A(f) from fct to fcc is 330 K, which seems to coincide with the result by the He vs. T curve. Shape memory effect vs. T curve had two sharp increasing points near 320 K and 400 K which correspond to the phase transformation temperatures estimated by X-ray, Hc and epsilon, respectively.