Analysis of Magneto-Optical Hysteresis Loops of Amorphous and Surface-Crystalline Fe-Based Ribbons.

Ondřej Životský,Jiří Buršík,Yvonna Jirásková,Kamila Hrabovská,Dmitry Markov

doi:10.3390/ma14010141

Abstract

Three Fe-based ribbon-type samples prepared by a conventional planar flow casting process are studied from the viewpoint of the amorphous Fe80Si4B16 and partially surface crystallized Fe80Si10B10, and Fe80.5Nb6.9B12.6, microstructures. Surface magnetic properties are investigated by magneto-optical Kerr microscopy, allowing the measurement of a local hysteresis loop from a selected area on the ribbon surface, and simultaneously, a domain structure corresponding to a definite point at the loop. For an amorphous sample, the changes in the slopes of hysteresis loops are related either to the size of the selected surface area, from which the loop is measured, or to the type, width, and movement of magnetic domains through this area. In the first case, the resizing of the area simulates an effect of changing the diameter of the incident laser beam on the magneto-optical properties of the ribbon. In the latter case, the observed wide-curved and fingerprint domains are responsible for markedly different shapes of the hysteresis loops at lower magnetic fields. If the surface is crystallized, the magnetic properties are more homogenous, showing typical one-jump magnetization reversal with less dependence on the size of the surface area. The magneto-optical experiments are completed by transmission electron microscopy and magnetic force microscopy.

Highlights

There is still increasing interest in the surface magnetic behavior of the materials in light of both fundamental research and applications [1]
X-ray diffraction (XRD) diffractograms and conversion electron Mössbauer spectrometry (CEMS) spectra confirmed an amorphous structure at the airsurface of the Fe80 Si4 B16 sample
The small surface crystallites are clearly seen in the transmission electron microscope (TEM) images; The best bulk soft magnetic properties are observed in the case of the anamorphous

Summary

Introduction

There is still increasing interest in the surface magnetic behavior of the materials in light of both fundamental research and applications [1]. To the scanning and transmission electron microscopies, or conversion electron Mössbauer spectrometry, the frequently-used non-destructive techniques for the surface magnetic characterization is the magneto-optical Kerr effect (MOKE). It is based on the change of the polarization of incident polarized light when reflected from the surface of the magnetized material. The magneto-optical method is concentrated on the selected surfaces of ribbon-type samples with the aim to explain different contributions detectable at MOKE loops and to compare the results from the viewpoint of different microstructures, amorphous and crystallized. The hitherto experiences indicate that the shape of the loop during the magnetization reversal strongly depends on the size of area from which the loop is measured and on the type of domain structure located in this area

Experimental Details

Microstructural and Bulk Magnetic Properties

Surface Magnetic Properties—Amorphous Fe80 Si4 B16 Ribbon

Selected

Magneto-optical

Conclusions