Study of the Induced Anisotropy in Field Annealed Hitperm Alloys by Mössbauer Spectroscopy and Kerr Microscopy

Abstract

Samples of Fe39Co39Nb6B15Cu1 alloy were nanocrystallized under zero field annealing (ZF) and transverse field annealing (TF) conditions. A reduction in coercivity for TF samples with respect to ZF sample (16 and 45 A/m, respectively) is observed. Kerr microscopy images show a well-defined parallel domain structure, transversally oriented to the ribbon axis for the TF sample unlike for the ZF sample, for which a complex pattern is observed with large and small domains at the surface of the ribbon. Although Mössbauer spectra are clearly different for the two studied samples, Mössbauer studies confirm that there is no significant difference between the hyperfine field distributions of TF and ZF samples but only the relative intensity of the 2 nd and 3 rd lines A23 (related to the angle between the gamma radiation and the magnetic moments, ). Whereas for TF annealed samples =90º (A23=4), indicating that the magnetic moments lay on the plane of the ribbon in agreement with the well-defined domain structure observed by Kerr microscopy, ZF annealed samples show A23=1.8. This value is close to that of a random orientation (A23=2) but smaller, indicating a slight preference for out of plane orientations. Moreover, it is clearly smaller than that of as-cast amorphous samples A23=2.8, with a preference to in plane orientations. The application of the law of approach to saturation yields a larger effect of the inhomogeneities in ZF sample with respect to TF one.

The Effects of Si Substitution with C on the Amorphous Forming Ability, Thermal Stability, and Magnetic Properties of an FeSiBPC Amorphous Alloy

“…This uniformity facilitates the movement of the magnetic domains and the rotation of the magnetic moments during alloy magnetization process. Blázquez et al [37] propose that, in Fe-based amorphous ribbons, there exists an inverse relationship between the coercivity and the width of magnetic domains, indicating that wider magnetic domains result in lower H c values. Moreover, in comparison to the C-2 alloy, the C-0 alloy exhibits a certain degree of bifurcation in its magnetic domains with increased irregularity.…”