"Information storage requirements continue to expand at rapid rates, fuelled by the growing use of computers for video and audio applications. Today, all hard disks contain platinum in their magnetic layers, compared with around 50 per cent in 1997. The proportion of platinum in the magnetic alloy has been increasing steadily over time, from less than 10 per cent five years ago to over 35 per cent, on average, today."
Source: http://www.platinum.matthey.com/applications/industrial-applications/hard-disks/
Source: http://www.platinum.matthey.com/applications/industrial-applications/hard-disks/