Š. Višňovský

Magneto-optical ellipsometry

Through the extension of the Yehs formalism (Surf. Sci.96 (1980) 41) to magnetic crystalline media the formulas of the magneto-optic ellipsometry and the dispersion relations for wave-guiding in multilayer magnetic crystalline structures are obtained. The theory covers most of the situations considered so far in the magneto-optics in which the optical response of the structures is linear in the amplitude of the incident wave. It is capable of treating the interfaces between two magnetic media and the structures containing such interfaces with no restrictions on the orientation of the magnetizations and crystalline axes at an arbitrary angle of incidence. The polar, longitudinal and transversal magnetizations in the structures are considered as special cases. Possible applications of the theory are in the analysis of the planar multilayer magneto-optic systems in the integrated optics and magneto-optic memory technology, in the study of profiles of magnetic surfaces subjected to mechanical wear, ion implantation, etc.

Magneto-optical Kerr spectra of nickel

Abstract The complex polar Kerr effect spectra (Kerr rotation and Kerr ellipticity) of high-purity ferromagnetic nickel are reported in the spectral range 1.5–5.2 eV. Freshly evaporated high optical quality Ni films, 90 nm thick, magnetically saturated perpendicular to the film plane served as sample surfaces. New extended spectroscopic information has been obtained. The agreement with the published data is discussed.

Physical properties of Al doped Ba hexagonal ferrite thin films

We developed the thin film microwave magnetic material, M-type barium hexagonal ferrite (BaM) doped with Al, for signal processing devices operating above 40 GHz with little to no applied magnetic field. Al was chosen as the dopant material because it significantly increases the already strong anisotropy field of BaM. A series of thin film BaAlxFe12-xO19 samples, x ranging from 0 to 2 in 0.25 steps, were deposited on Pt templates using a metal-organic decomposition growth technique. The resulting films are polycrystalline and highly textured, with the hexagonal c-axis directed out of plane. These films are also self-biasing; easy axis hysteresis loops have a high squareness ratio, s, in the 0.83-0.92 range. As expected, the anisotropy field increases with x, ranging from 1.34 to 2.19 × 106 A/m (16.9-27.5 kOe) for x = 0-2, while the saturation magnetization Ms decreases with x, ranging from 0.334 to 0.175 × 106 A/m (4πMs = 4.2-2.2 kG) for x = 0-2. These values were measured at room temperature, but the tem...

OPTICS OF MAGNETIC MULTILAYERS

Optical response of layered lossy anisotropic media displaying magnetic order is considered. The analysis is based on classical optical terms. Planar magnetic multilayers (ML) are represented by Yehs 4×4 matrices which relate the field amplitudes in the isotropic half spaces on both sides of a ML structure. Each layer is characterized by a complex permittivity tensor of general form while magnetic permeability assumes its vacuum value. The basic assumption is that the electromagnetic field in a layer can be represented by a linear combination of four eigenmodes following from the wave equation of the layer. Then the boundary conditions at interfaces along with a set of four field amplitudes completely determine ML electric and magnetic field distributions. Alternatively, two orthogonally polarized incident wave amplitudes in each of the isotropic half spaces may be specified. The approach is more general than those published so far. Assuming minimum previous experience in the ML optics the case of polar magnetization is treated in detail to provide a simple way to the solution of the problems most often encountered in practice.

Effect of multiple internal reflections on Faraday rotation in multilayer structures

A simple procedure is presented for computing optical transmission and Faraday‐rotation optical density (OD) planar layered structures when all internal reflections are taken into account. The procedure makes use of the Mueller matrix technique and assumes that interference effects, Faraday ellipticity, and boundary magneto‐optical effects, e.g., Kerr effect, are not important. The general formulas are applied to the case of the three‐layer structure from which two examples of some practical interest are derived, i.e., a single absorbing layer on a nonabsorbing substrate and two identical absorbing layers on either side of a nonabsorbing substrate. The solutions are substantially simplified when Faraday‐rotation angles are small.

Magneto-optical effects in ultrathin structures at transversal magnetization

Procedures based on the Yeh’s 4 × 4 matrix formalism for the treatment of the electromagnetic interactions in multilayers at transversal magnetization and at an arbitrary angle of incidence are described. With the restriction to the magneto-optical effects linear in the magnetization the characteristic matrix for magnetic layer is derived. The reflection and transmission coefficients are obtained in the case of magnetic ultrathin film on substrate. The magneto-optical thin film waveguides at transversal magnetization are analysed in details and the dispersion relations for guided modes in a single layer, a bilayer, a sandwich and the approach to expand this way for waveguiding conditions in multilayers are presented.

Magneto-optical contribution of interfaces in ultrathin film Au/Co/Au structures

Abstract Magneto-optical (MO) polar Kerr rotation (PKR) and ellipticity (PKE) spectroscopic studies of Au(5 nm)/Co(0.4–1.8 nm)/Au(25 nm) ultrathin film sandwiches showed that the spectra can be represented as a sum of two components: one (nearly) linearly dependent plus one independent of the Co layer thickness, t Co . The two components were determined from the experiments on well defined sandwiches with stepped wedge Co layers after eliminating the MO contribution from the glass substrate and sandwiching the Au layers. Two effects responsible for the t Co -independent components: (1) spin polarization in the Au monolayers adjacent to Co and (2) roughness at AuCo interfaces were considered. The results of modelling and a comparison with MO spectra of gold suggest that latter effect is dominant.

Magneto-optical effects in crystals at the normal incidence

We consider the interaction of a polarized electromagnetic wave in a magnetically ordered crystal plate surrounded by an isotropic ambient at the normal incidence. The crystalline medium of the plate is specified by the general non-symmetric permittivity tensor. The results are expressed in terms of the transmission and reflection matrices which relate the electric fields of the incident wave to those of transmitted and reflected waves. Their applications are illustrated by examples of an isotropic plate magnetized normal to the interface, a cubic crystal magnetized parallel to the interface and an orthorhombic crystal magnetized along the axis normal to the interface. The effect of the reflection from the interfaces and the interference effect are included. The paper treats the reflection at an interface between an isotropic ambient and an absorbing magnetic crystal at small non-zero angles of incidence. The general reflection matrix is applied to the determination of the magneto-optical effects quadratic in magnetization.

Magneto-optic ellipsometry in exchange-coupled films.

Analytical representations of Jones matrices for the magneto-optic (MO) reflection in (a) a magnetic film on a magnetic substrate separated by a nonmagnetic spacer and (b) two ultrathin magnetic films separated by a nonmagnetic spacer, sandwiched between a nonmagnetic cover and a nonmagnetic substrate with arbitrary and independent orientations of magnetization, are provided. Originally isotropic media subjected to a uniform magnetization are considered. The discussion of MO response is restricted to the terms linear in the off-diagonal permittivity tensor elements, and typical situationsare illustrated numerically. The results are useful for the analysis of the experiments in MO ellipsometry and MO magnetometry of exchange-coupled magnetic ultrathin-film structures.

Magneto-optical polar Kerr effect in a film-substrate system

The problem of electromagnetic reflection at an arbitrary angle of incidence in a system consisting of an isotropic ambient, a magnetic film and a thick magnetic substrate is studied. The magnetizations in both the film and substrate are assumed normal to the planar interfaces. The results are expressed in terms of the reflection matrix which is directly connected to the experimentally observed quantities: ellipsometric ratio and magneto-optical rotation and ellipticity. The general condition for guided wave propagation in the system is obtained. The theory is applied to the special cases of (a) normal incidence, (b) oblique incidence on a uniaxial film on a uniaxial substrate, both optical axes being normal to the interfaces, and (c) oblique incidence on a system consisting of an isotropic ambient, a magnetic film and a thick magnetic substrate assuming the diagonal elements of the permittivity tensor in a particular magnetic medium (film or substrate) equal to each other and the corresponding off-diagonal elements much smaller with respect to them. The possible practical applications of the present analysis are in the optimum design of film-substrate structures in magneto-optic devices and in the optical studies of the surface effects in magnetic materials.