Applications of the magneto-optical Kerr effect to studies of stratified magnetic media.

Abstract

Three applications of Smith's model of magneto-optical effects in stratified magnetic media are presented. Each application involves the incident-angle dependence of magneto-optical effects which Smith's model treats explicitly. In addition. the three applications address current issues in magnetic and magneto-optical recording. The first problem considered is that of nonmagnetic surface layers which form on magnetic recording heads. The second is a theoretical treatment of effects which arise in magneto-optical recording when high numerical-aperture optical systems are combined with media exhibiting interference-enhanced optical properties. The final application is a novel technique for determining the entire dielectric tensor of materials used for magneto-optical recording. The incident-angle dependence of the longitudinal Kerr effect is employed to study nonmagnetic surface layers which form on ferrite recording heads. Calculations based on the Smith model show a correlation between the inert-layer thickness and the incident-angle dependence of the longitudinal Kerr effect. Experimental results confirm the shift in the angular position of the signal peak. in agreement with the theory for finite inert-layer thickness. An unambiguous determination of the inert-layer thickness for ferrite materials is prevented because of a periodic dependence of the peak angle on the inert-layer thickness. Jones-matrix algebra is used with the Smith model to quantitatively determine the effects of obliquely-incident rays on the reflectance and magneto-optical readout signals for various magneto-optical media structures. The most antireflective structure is found to be very sensitive to incident-angle effects. Structures with moderate reflectance (>10%). however. are not significantly affected by incident-angle effects. Finally. a technique for the determination of the optical and magneto-optical constants from multiple incident-angle measurements of reflectance and Kerr rotation is presented. The experimental system employs a Helium-Neon laser and a rotating differential detection system. The technique is used to investigate the optical properties of a series of Cu/Co multilayers and a comparison with a model based on the bulk optical. constants of Cu and Co is made. Anomalous behavior is observed for multilayers with very thin periods.