Mossbauer study of magnetic properties and structure of amorphous Fe-(Co,Cr)-Zr alloys

Mossbauer spectroscopy was used to study the effects of composition, temperature, hydrogenation, external magnetic field on series of amorphous Fe90-xCoxZr10 (x = 4, 10,..., 70) and Fe90-yCryZr10 (y = 0, 4, 7, 13, 16, 20) alloys. Magnetic anisotropy and moment distributions in terms of an expansion in spherical harmonies were analyzed. The results reveal the following facts: (i) The hyperfine field distributions P(H-hr)-H-hf of a-Fe90-xCoxZr10 (x = 4, 10, 20) and Fe90-yCryZr10 (y = 0, 4, 7, 13, 16) comprise two or three Gaussian distributions, the low-field and high-field spin fractions obtained from the fitting of P(H-hf)-H-hf curve are changed by Co(Cr) content, temperature, applied magnetic field and hydrogenation. (ii) Anomalous behaviors are found in Co(Cr)-poor Fe-(Co, Cr)Zr alloys, which means the existence of Invar effect and spin-grasslike behavior. (iii) Hydrogenation gives rise to the drastic changes of the hyperfine parameters, which can mainly be associated with the volume and hybridization effect (iv) The moment distributions of a-Fe90-xCoxZr10 (x = 4, 10, 20, 30, 40) are preferentially in the direction of the film length. A 90 degrees-type magnetic coupling between spin-clusters in 3DFM and in FSC may exist in Co(Cr)-poor Fe-(Co, Cr)-Zr alloys. A "3DFM+FS+FSC" model containing density inhomogeneity provides a rather satisfactory explanation.