Magnetic behavior and microstructure of Finemet-type ribbons in both, surface and bulk

Abstract

Different kinds of magnetic anisotropies have been induced during the nanocrystallization process of Co- and Ni-rich amorphous ferromagnetic (Finemet) ribbons using diverse procedures like the application of a constant stress or an axial magnetic field during the annealing process. Magnetization measurements have evidenced the anisotropy of the treated samples. The main goal of this work has been the structural and microstructural analysis of the treated ribbons using X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM), detecting substantial differences in the crystallization state and grain size of the samples depending on the treatment that was carried out. Moreover, AFM measurements revealed in all the treated samples a strong nanocrystallization of the surface without evidences of amorphous matrix, which contrast with XRD measurements that have shown a high content of amorphous phase in the bulk of the ribbons. Magneto-optical Kerr effect measurements have been performed with the aim to elucidate the complex magnetic behavior that is expected for the surface of the ribbons, measuring surface hysteresis loops that show much higher coercive field values than in the bulk.