Analytical TEM Examinations of CoPt-TiO₂ Perpendicular Magnetic Recording Media

Abstract

For this analytical TEM study, nonmagnetic oxygen-rich boundaries were introduced into Co-Pt-alloy perpendicular recording media by cosputtering Co and Pt with TiO2. Increasing the TiO2 content resulted in changes to the microstructure and elemental distribution within grains and boundaries in these films. EFTEM imaging was used to generate composition maps spanning many tens of grains, thereby giving an overall depiction of the changes in elemental distribution occurring with increasing TiO2 content. Comparing EFTEM with spectrum-imaging maps created by high-resolution STEM with EDXS and EELS enabled both corroboration of EFTEM results and quantification of the chemical composition within individual grain boundary areas. The difficulty of interpreting data from EDXS for these extremely thin films is discussed. Increasing the TiO2 content of the media was found to create more uniformly wide Ti- and O-rich grain boundaries as well as Ti- and O-rich regions within grains.

Topology and elemental distribution in Co alloy:oxide perpendicular media

“…The images are in agreement with those of CoPt: TiO x in Ref. 1 and show best the dark regions ͑"cavities"͒ in the interior of the grains at ␣ = 15.60°. As the specimen is tilted by increasing ␣, the three-dimensional ͑3D͒ cylindrical dome shape of grains becomes more apparent.…”

“…It was reported that "low mass-thickness pockets" are present in the interior of many grains of the CoPt: TiO 2 media. 1 Other researchers observed "white dots" in BF of CoCrPt: SiO x media when the oxygen percent is high ͑21 at. %͒.…”

“…There have been many studies on reducing the grain size and better isolation with various oxides. [1][2][3][4][5][6] In order to investigate the microstructure including grain size and oxide isolation in media, bright field ͑BF͒ conventional transmission electron microscopy ͑CTEM͒ has been commonly used. However, these BF images provide superimposed phase, mass-thickness, and diffraction contrast information.…”

Aberration-Corrected Transmission Electron Microscopy of the Intergranular Phase in Magnetic Recording Media

“…We have shown that the ML grain structure produced in this way has a one-to-one agreement with the Ru seed layer grains. 10 Plan-view TEM specimens are prepared using a conventional method: 10,22 After the initial grinding and polishing of each sample from the back side, standard 3 mm diameter TEM specimen disks are punched out. These samples are then further ground using a Gatan-656 dimple grinder from the same side to reach a thickness of less than 15 μm at the center.…”

Composition Mapping of Co-Pt-Ti-O Perpendicular Magnetic Recording Media by Simultaneous EDS and EELS Spectrum Imaging

“…1; the structure consists of sub-10-nm grains of Co-Pt with Ti-and O-rich intergranular regions (quantitative EELS yields a stoichiometry near TiO 2 ), containing essentially no Pt but significant amounts of Co, and intragranular pockets enriched in Ti and O. Characterization of the additional materials yields the dependence of structure on TiO 2 content that is essential for structure-magnetic property correlations [5,6]. The results clearly demonstrate the advantages of combined EDS and EELS spectrum imaging: EDS can analyze elements such as Pt that are not amenable to EELS analysis because of ionization-edge shape, energy, or cross-section; EELS provides much better signal-to-noise for major constituents and can potentially supply information on valence.…”