Quantitative Composition Maps of Magnetic Recording Media by EFTEM

Abstract

Elemental mapping of Co-Cr-X based magnetic recording media at resolutions approaching 1 nm by energy-filtered transmission electron microscopy (EFTEM) can provide quantitative measurements of intergranular Cr segregation for correlation with magnetic properties and materials processing. The thin-film media present many challenges for EFTEM methods, such as diffraction contrast and closelyspaced edges. The goal of this work was to provide robust methods for mapping quantitative compositions in such materials. Results presented here are for a model material of 60 nm of Co84Cr12Ta4 on a 75 nm Cr underlayer; both films were d.c. magnetron sputtered onto a NiP-plated Al substrate pre-heated to 250°C. Other compositions and thinner layers (∼30 nm) have also been studied. EFTEM was performed on back-thinned, plan-view specimens with a Gatan Imaging Filter (GIF) interfaced to a 300 kV LaB6 Philips CM30. Optimized acquisition conditions have been detailed elsewhere. Besides core-loss image series, zero-loss I0 (slit width Δ=10eV), low-loss Ik (Δ=30eV), and unfiltered IT images were recorded, and maps of t/λ. = ln(IT / I0), where t is specimen thickness and λ. is the total inelastic mean free path, were produced.