Sensitive magneto-optical sensors for visualization of magnetic fields using garnet films of specific orientations

Abstract

Garnet films of high Faraday rotation are applied as magneto-optical sensors to visualize the spatial distribution of magnetic fields. Using specific orientations, the induced anisotropy can generate an easy plane of magnetization which is inclined with respect to the film plane. If the magnetization lies in this plane a very high sensitivity can be achieved. The dependence of the geometrical orientation of the easy plane on the growth direction is calculated and the sensitivity and dynamic range are derived. Experimental results of a [112] oriented garnet film are in good agreement with calculations.

Novel Magnetic Photonic Crystal Structures for Magnetic Field Sensors and Visualizers

“…The transfer matrices are determined by the layers thicknesses and their dielectric tensor. While nonmagnetic constituents of MPC can be usually regarded as isotropic media having a diagonal dielectric tensor, magnetic layers are described by the magnetization-dependent nondiagonal tensor, which is for the case of the magnetization directed along -axis given by (4) where the gyration, , and dielectric constant, , depend on the magnetization, with and vanishing at zero magnetization. This implies that optical anisotropy for such materials is purely magnetic field-induced [1].…”

“…To characterize the performance of a MO sensor with in-plane magnetization, its photo-response (P/R) characteristic is used [4]: (1) where and are the incident (plane-polarized) optical intensity and output optical intensity detected after passing through the analyzer oriented at 45 with respect to the input polarization plane, respectively, and are the specific 0018-9464/$25.00 © 2008 IEEE Faraday rotation of the sensing film and the film thickness, and is the absorption coefficient of the film material. The term is equal to , where is the measured component of magnetic induction applied in the direction perpendicular to the film plane, is the magnetic induction necessary to saturate the magnetization in the film along the film normal, and is the angle between the film normal and the magnetization vector .…”

“…On the other hand, the sensitivity is given by [4] (2) Thus, the higher the sensitivity, the lower the dynamic range is, and vice versa. To obtain high sensitivity, must be small and must be large.…”

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].…”

“…If a sensor is based on a film with the perpendicular direction of the magnetization with respect to the film plane, such a film possesses a maze-like or stripe domain structure. To characterize the performance of MO sensors with in-plane magnetization, the photo-response (P/R) characteristic reported by Klank et al is adopted [4]:…”