Magnetostrictive properties of amorphous and crystalline TbDyFe thin films

Abstract

Abstract A series of amorphous and partially crystalline giant magnetostrictive thin films of the composition (Tb 0.3 Dy 0.7 ) 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 °C. 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 °C were amorphous. Crystallization started at T s =425 °C. The magnetostrictive coefficient λ , 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 °C. The hysteresis loops of the amorphous samples presented close to zero coercivities. These samples showed λ ≅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 ≥425 °C showed λ max ≅350–750 ppm but the magnetostrictive curve was much broader (a non-linear butterfly shape) and shifted to the value of H c .