Magnetic, Mossbauer and magnetostrictive studies of amorphous Tb(Fe0.55Co0.45)(1.5) films

The Tb(Fe0.55Co0.45)(1.5) films were fabricated by rf magnetron sputtering from a composite target. Samples were investigated by means of x-ray diffra ction, vibrating sample magnetometer, conversion electron Mossbauer spectra , and magnetostriction measurements. The as-deposited film is an amorphous alloy with a perpendicular magnetic anisotropy and an intrinsic magnetostri ction lambda = 1080 x 10(-6) in an applied field of 0.7 T. In this state, i t was determined that the hyperfine field B-hf = 23.5 T and the cone-angle between the Fe moment direction and the film-normal direction beta = 12 deg rees. After annealing in the temperature range of T-A = 250-450 degrees C t he amorphous structure still remained, however the anisotropy was changed t o a parallel one. The soft magnetostrictive behavior has also been improved by these heat treatments: the parallel magnetostriction lambda(parallel to ) = 465 x 10(-6) was almost developed in low applied fields of less than 0. 1 T and, especially, a huge magnetostrictive susceptibility chi(lambda) = d lambda(parallel to)/d(mu(0)H) = 1.8 x 10(-2) T-1 was obtained at mu(0)H = 15 mT. (C) 2000 American Institute of Physics. [S0021-8979(00)06210-1].