Magnetostrictive properties of amorphous and crystalline TbDyFe thin films

A series of amorphous and partially crystalline giant magnetostrictive thin films of the composition (Tb0.3Dy0.7)(40)Fe-60 have been prepared by DC magnetron sputtering. The sputtering conditions were the same for all samples apart from the substrate temperature, T-s, which varied between 330 and 510 degreesC. The crystalline state, the magnetic and the mechanical properties of those films were investigated in relation to the substrate temperature. Films deposited at 330-400 degreesC were amorphous. Crystallization started at T-s = 425 degreesC. The magnetostrictive coefficient lambda, at 4 kOe and at room temperature increased with increasing T-s from 185 to 750 ppm at H-max. This was related to an increase of the Curie temperature, T-C, from 35 to 315 degreesC. The hysteresis loops of the amorphous samples presented close to zero coercivities. These samples showed lambda congruent to 300 ppm in a field of 1000 Oe. The direction of the magnetic moments in the amorphous state films changed gradually from perpendicular to parallel to the film plane with increasing T-s. The samples were deposited at T-s greater than or equal to 425 degreesC showed lambda(max) congruent to 350-750 ppm but the magnetostrictive curve was much broader (a non-linear butterfly shape) and shifted to the value of H-c. (C) 2003 Elsevier B.V. All rights reserved.