E. R. Moog

Universal approach to magneto-optics☆

Magneto-optics is described in a unique framework. Reflection and transmission of a general multilayer system is expressed by means of medium boundary and propagation matrices which are universal and apply to any configuration of films and media. The results for the magneto-optic coefficients are cast in the form of sets of four linear, inhomogeneous equations. It is shown that in the thin-film limit, the Kerr effect obeys an additivity law for a system consisting of any number of magnetic films. Computer simulations were performed on different film-configurations, including an overlayer, a sandwich and a superlattice.

Magnetic properties of novel epitaxial films (invited)

The surface magneto‐optic Kerr effect (SMOKE) is used to explore the magnetism of ultra thin Fe films extending into the monolayer regime. Both bcc α‐Fe and fcc γ‐Fe single‐crystalline, multilayer films are prepared on the bulk‐terminated (1×1) structures of Au(100) and Cu(100), respectively. The characterizations of epitaxy and growth mode are performed using low‐energy electron diffraction and Auger electron spectroscopy. Monolayer range Fe/Au(100) is ferromagnetic with a lower Curie temperature than bulk α‐Fe. The controversial γ‐Fe/Cu(100) system exhibits a striking, metastable, surface magnetic phase at temperatures above room temperature, but does not exhibit bulk ferromagnetism.

Fundamental magneto‐optics

The reflection‐transmission problem is considered for light from a boundary between two magnetic media with arbitrary direction of the magnetization within each medium. Explicit formulas are derived for the magneto‐optic coefficients.

Kerr effect from Pt/Co superlattices and the role of the magneto-optic activity of Pt

The magneto‐optic response of Pt/Co superlattices is simulated to gain insight into the recent experimental findings of favorable information‐storage characteristics. Major trends are reproduced qualitatively, and the calculations indicate that the Pt contributes significantly to the short‐wavelength polar Kerr signal (at 4 eV). The influences of the wavelength, angle of incidence, component thicknesses, overcoat, and substrate on the rotation, ellipticity, and reflectivity are evaluated.

Role of the substrate in enhancing the magneto‐optic response of ultrathin films: Fe on Au

Simulations are presented for the magneto‐optic rotation and ellipticity as a function of Fe thickness in the 0–400 A range for the system Fe on Auu2009(100). The results, which are based on tabulated bulk optical constants, agree with recent experiments and explicitly demonstrate the role of the Au underlayer in enhancing the signal from the ferromagnetic overlayer.

Polar Kerr-effect observation of perpendicular surface anisotropy for ultrathin ferromagnetic films: Fcc Fe/Cu(100)

Etude par effet Kerr polaire et longitudinal de linfluence de lepaisseur de la couche et de la temperature de croissance sur les proprietes magnetiques

Additivity of the Kerr effect in thin-film magnetic systems☆

Abstract A universal approach is developed for calculating magneto-optic coefficients in multimedia systems. Three configurations are described: (i) a two-media, one-boundary system, (ii) a film sandwiched between two media and (iii) a multilayer system, such as a superlattice or even a randomly stacked sequence. It is proven that in the thin-film limit, the Kerr effect for a multilayer system obeys an additivity law: it is equal to the algebraic sum of the Kerr signals of the individual magnetic films in the system. The prediction is verified experimentally and in numerical calculations on an Fe/Cu/Fe 3-layer stack grown on a Pd-substrate.

Analysis of Kerr rotation from Cu/Co, Pd/Co, and Pt/Co superlattices

Numerical simulations of the Kerr signals from Cu/Co, Pd/Co, and Pt/Co superlattices show, in general, a scaling of the signal with the amount of Co in the superlattice. Experimentally, however, the signal from Pt/Co superlattices at ∼4 eV is larger than that from bulk Co, despite the lesser total amount of Co. This is due to the magnetization induced in the Pt by the Co. Comparison of the Pd/Co and Pt/Co results with experiment indicates that the magnetization induced in the Pt by the Co plays a more important role in the magneto‐optic activity than does the induced magnetization of Pd.

Elementary formula for the magneto‐optic Kerr effect from model superlattices

An elementary formula is derived for the magneto‐optic Kerr effect from model superlattices. An exact result is obtained for the case of equal refractive indices for the two constituents of the superlattice. Co/Pt is used as an example of such superlattices for wavelengths in the vicinity of 2 eV. First‐order corrections in the difference of the refractive indices are derived which are suitable for treating a variety of materials.

Transverse magneto-optic Kerr effect in ultrathin films☆

Abstract The behavior of the magneto-optic Kerr effect is simulated for ultrathin Fe/Au overlayers and superlattices with magnetization direction varying from polar to transverse configurations. The simulations are based on a general macroscopic formalism, introduced previously, that can treat arbitrary directions of the magnetization, and that utilizes tabulated bulk optical and magneto-optical parameters. Simulations for Co overlayers on Cu are also presented and compared to published transverse Kerr effect data for monolayer-range Co/Cu(100). Transverse Kerr effect measurements at the He-Ne wavelength are presented for a series of ∼ 500 A thick, sputtered Fe/Mo superlattices, whose component layer thicknesses are fixed at 25 A of Fe, and range from 4 to 36 A for the Mo layers. The Co/Cu and Fe/Mo data are compared to simulation to evaluate the applicability of the macroscopic approach to describe the ultrathin regime.