Magneto-optical visualization of metal-loss defects in a ferromagnetic plate: experimental verification of theoretical modeling

Abstract

Rare-earth iron garnet films with in-plane magnetic anisotropy grown on [111]-oriented substrates are promising for the visualization of magnetic leakage fields in nondestructive evaluation. Such magneto-optical films have to be specifically engineered, and we give an example of this technology. To assess the validity and accuracy of finite-element calculations of a magnetization assembly combined with the physical modeling of the image formation, comparisons between calculated and experimentally obtained magneto-optical images of metal-loss defects have been made. A convincing quantitative agreement is demonstrated. It is shown that both physical and computer modeling techniques allow for a predictive engineering design of the prospective applications and provide greater insight into the method.

Novel Magnetic Photonic Crystal Structures for Magnetic Field Sensors and Visualizers

“…The relationship between the width of the magnetic domains, the thickness of the magnetic film and the characteristic length of the magnetic material is described by the relationship (3) where is the period of the domain structure , where and are the widths of the domains with the up and down direction of the magnetization [10].…”

“…The in-plane magnetized films usually provide more flexibility for the characterization of objects under investigation. At the same time, films possessing the maze-like domain structure and small saturating magnetic fields are more suitable for detecting localized magnetic defects in ferromagnetic samples [3]. The films with inclined magnetization direction are rarely mentioned, nevertheless, due to their excellent linearity, they are very suitable in magnetic field measurement systems.…”

Faraday rotation and sensitivity of (100) bismuth-substituted ferrite garnet films

“…If a light beam propagates along the z-axis through the magnetic film, then the polar Faraday rotation of the film is given by (neglecting the Voigt-effect and multiple reflections) [17] …”

Magnetic field sensors and visualizers using magnetic photonic crystals

“…Magneto-optical (MO) imaging and sensing devices utilizing Bi-substituted iron garnet films are widely used to examine the spatial distribution of magnetic fields produced by magnetized objects [1][2][3][4][5], to study the vortex matter in hightemperature superconductors [6], and as current sensors [7]. Depending on the properties of the objects under study, the sensing films with in-plane, inclined, and perpendicular orientation of the magnetization vector with respect to the film plane are used [1].…”

“…The in-plane magnetized films usually provide good flexibility for the characterization of objects under study. At the same time, films possessing the maze-like domain structure and small saturating magnetic fields are more suitable for detecting localized magnetic defects in ferromagnetic samples [3].…”