HDDs are used for large amounts of storage, and so need high areal density on the platter than stores the data. The space between the platter and the read head is getting smaller and smaller, limiting the thickness of materials that can be used.
Carbon-based overcoats (COCs) are currently used to protect platters from mechanical damages and corrosion, and over the years have reduced in thickness from 12.5nm to around 3nm as the areal density increased to 1Tbyte/in2
The researchers at the Cambridge Graphene Centre were part of a global team that replaced commercial COCs with one to four layers of graphene, and tested friction, wear, corrosion, thermal stability, and lubricant compatibility.
Graphene has the ideal properties of an HDD overcoat in terms of corrosion protection, low friction, wear resistance, hardness, lubricant compatibility, and surface smoothness in a single atomic layer. This halves in friction and provides better corrosion and wear than state-of-the-art solutions, reducing corrosion by 2.5 times.
The researchers transferred graphene onto hard disks made of iron-platinum as the magnetic recording layer, and tested Heat-Assisted Magnetic Recording (HAMR) which increases the storage density by heating the recording layer to high temperatures. Current COCs do not perform at these high temperatures, hence the need for a new material such as graphene. This gave a data density higher than 10 terabytes per square inch.
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“Demonstrating that graphene can serve as protective coating for conventional hard disk drives and that it is able to withstand HAMR conditions is a very important result. This will further push the development of novel high areal density hard disk drives,” said Dr Anna Ott from the Cambridge Graphene Centre, one of the co-authors of this study.
“This work showcases the excellent mechanical, corrosion and wear resistance properties of graphene for ultra-high storage density magnetic media. Considering that in 2020, around 1 billion terabytes of fresh HDD storage was produced, these results indicate a route for mass application of graphene in cutting-edge technologies,” said Professor Andrea C. Ferrari, Director of the Cambridge Graphene Centre.
The team included researchers from CSIR-Advanced Materials and Processes Research Institute, Bhopal, India, as well as the Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore, the Center for Nanoscale Materials, Argonne National Laboratory in the US as well as EPFL and EMPA in Switzerland.
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