Effects of heteroepitaxial strain on Laves phases TbFe2 and DyFe2

(110) oriented growth was observed for thin films of the highly magnetostrictive Laves phases TbFe2 and DyFe2 on Ta (110). On Nb (111), TbFe2 nucleates in the (111) orientation. Depending on the substrate temperature during growth, varying degrees of residual tensile strain were observed in the films. For TbFe2 grown on Ta (110) at 680 degrees C, x-ray diffraction revealed a splitting of the (220) Bragg reflection into a strain free component structurally coherent with the template, and a component with 0.5% biaxial tensile strain at room temperature. This strained component can be attributed to the difference in thermal expansion between the sapphire substrate and the TbFe2 film. Magnetic hysteresis measurements revealed that the axis of easy magnetization lies in the film plane for both (110) and (111) oriented samples. (C) 1998 American Institute of Physics. [S0021-8979(98)25411-9].