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METALLIC OVERLAYER FOR CoP PROTECTION IN THIN FILM DISKS

IP.com Disclosure Number: IPCOM000035699D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Brusic, VA: AUTHOR [+4]

Abstract

A thin layer, 5 to 10 nm in thickness, of zirconium or hafnium, sandwiched between the magnetic CoP layer and the overcoat, significantly improves the corrosion resistance of the thin film disk.

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METALLIC OVERLAYER FOR CoP PROTECTION IN THIN FILM DISKS

A thin layer, 5 to 10 nm in thickness, of zirconium or hafnium, sandwiched between the magnetic CoP layer and the overcoat, significantly improves the corrosion resistance of the thin film disk.

Although metallic cobalt and CoP can form several oxides, they are not particularly protective and in most natural environments cobalt readily corrodes. Moreover, in a typical disk structure, CoP is covered by a thin layer of C (deposited by RF or DC sputtering to provide desired mechanical properties) which is conductive and accelerates CoP corrosion through a galvanic attack at sites of incomplete coverage. Thus, there is a concern about disk's stability in storage as well as in files, which are not hermetically sealed and which operate at humidities above 30 percent.

Thin film interlayers of zirconium or hafnium for enhanced disk corrosion resistance were selected after carefully screening several factors. The interlayer has to be thin and any metal more noble than CoP could cause local galvanic attack of the unprotected area. Thus, among many thin films of metals known to passivate [*] and examined by electrochemical tests in DI water, advantage is given to zirconium, hafnium, aluminum and vanadium. They show low corrosion rates, and corrosion potentials lower than that of CoP. The preference is given to Zr and Hf because they protect not only against water but also against more acidic pollutants (Cl2, H2S, SO2,...