Degradation of very high density data tape recording heads

Although data tape drives are never seen on a PC now, tape is still the most convenient and most cost effective way of storing very large amounts of data when access time is not an important consideration. In addition to this tape is the safest way of archiving a data. Because of this the data drives are used extensively, for example in the finance, insurance and banking industries and in any large server were frequent automatic file back-up is essential. The magnetic storage industry is growing at a cumulative rate of about 10% per year with a present market estimated at over £50 billion per year. The tape drive industry is a major contributor to this world-wide market with a market share of almost £6 billion. Therefore tape storage systems are an important sector in the data storage industry. This will only continue to be so, however, if storage capacity (the amount of data stored per unit area) is continually improved.

Storage capacity, however, is limited by recession of the metal recording poles below the surface level of the read/write head due to differential wear. This causes spacing between the magnetic recording media and the active part of the head, the read/write poles, which leads to a fall in the magnetic signal which in turn limits the amount of information which can be stored in a given area. This recession must, therefore, be eliminated if the data tape storage industry is to survive in the longer term.

The thin film heads consists of an Al2O3/ TiC ceramic tape bearing surface surrounding metal poles set in an Al2O3 insulator. AES examination of the surfaces of worn heads has isolated sub micron Ti containing particles. These particles are dragged across the head causing nano-abrassive wear, which, since the poles are softer than other components of the head, leads to the poles being recessed and loss of signal.

The only source of the Ti containing particles is the ceramic tape bearing surface. Further examination of the Al2O3/ TiC ceramic by XPS has determined the mechanism of formation of these abrasive particles. This is due to tribo-oxidation of the TiC grains in the ceramic to form a TiO2 oxide layer about 30 nm thick, which then delaminates to form abrasive wear particles.

From the investigation we were able to identify the mechanisms of wear in these recording heads and recommend to the manufacturer to change the ceramic material of the tape bearing surface to a single phase aluminium or titanium oxide material.

The above illustrates the use of MSA analytical techniques in the investigation and isolation of wear and wear mechanisms and the subsequent suggestions of solutions to specific wear problems on the nano-scale. The techniques are equally useful in the investigation of tribology of components on the micro and macro scale under dry and lubricated conditions. Surface chemical interactions can easily be identified, leading to the understanding of a particular tribological problem hence the identification of a solution. Thus the MSA service can be invaluable to identify cause of component failure and in R&D in the evolution of next generation systems, materials and components.

One of the principals of the company, John Sullivan, has over 30 years experience in the use of surface analytical techniques in the solution of tribological problems for industry.

Typical tape-head ceramic material - made of two phase AlTiC (Al2O3-TiC) ceramic, the Auger mapping shows Ti and Al locations.

Ti 2p XPS spectra for the two phase AlTiC ceramic wear analysis during the similar wear condition, major different is relative humidity during wear test, the absolute water content increases from a to e (e is maximum). The Ti 2p3/2 peaks at 454.0eV and 458.3eV are due to TiC and TiO2 respectively. Peaks at 460eV and 464.0eV are the corresponding Ti2p1/2 peaks for these compounds.

Three-body particles were observed in the head poles region (AFM images), AES confirmed these particles are Ti-bearing Particles.

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