Magnetic, Mössbauer 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 diffraction, vibrating sample magnetometer, conversion electron Mössbauer spectra, and magnetostriction measurements. The as-deposited film is an amorphous alloy with a perpendicular magnetic anisotropy and an intrinsic magnetostriction λ=1080×10−6 in an applied field of 0.7 T. In this state, it was determined that the hyperfine field Bhf=23.5 T and the cone-angle between the Fe moment direction and the film-normal direction β=12°. After annealing in the temperature range of TA=250–450 °C the amorphous structure still remained, however the anisotropy was changed to a parallel one. The soft magnetostrictive behavior has also been improved by these heat treatments: the parallel magnetostriction λ∥=465×10−6 was almost developed in low applied fields of less than 0.1 T and, especially, a huge magnetostrictive susceptibility χλ=dλ∥/d(μ0H)=1.8×10−2 T−1 was obtained at μ0H=15 mT.