HDDs first appeared in the 1950s, but their use as storage devices in personal computers only took off from the mid-1980s. They have become ever smaller in size, and denser in terms of the number of stored bytes.
HDDs contain two major components: platters and a head. Data are written on the platters using a magnetic head, which moves rapidly above the platters as they spin. The space between head and platter is continually decreasing to enable higher densities. Currently, carbon-based overcoats (COCs) – layers used to protect the platters from mechanical damages and corrosion – occupy a significant part of this spacing.
The data density of HDDs has quadrupled since 1990, and the overcoats’ thickness was reduced from 12.5nm to about 3nm, which corresponds to one Tb/in2. However, a COCs’ thickness of less than one nm would be required to make a significant improvement in data storage and reach a density of 10 Tb/in2.
Since the current COCs lose most of their appealing properties under 2nm, Graphene Flagship researchers replaced them with one to four layers of graphene, and tested friction, wear, corrosion, thermal stability and lubricant compatibility. Beyond its unbeatable thinness, graphene fulfills all the ideal properties of an HDD overcoat: corrosion protection, low friction, wear resistance, hardness, lubricant compatibility and surface smoothness.
The researchers verified that graphene enables two-fold reduction in friction and provides better corrosion and wear than state-of-the-art COCs. A single graphene layer reduces corrosion by 2.5 times, and multilayer graphene showed excellent performance with a decrease of wear rate by three orders of magnitude.
“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 Anna Ott, from the Cambridge Graphene Centre, one of the authors of this study, currently based at the Graphene Flagship Associate Member the University of Exeter, UK.
Mar García-Hernández, Graphene Flagship Leader for Enabling Materials, says: “A jump in HDDs’ data density by a factor of ten and a significant reduction in wear rate are critical to achieve more sustainable and durable magnetic data recording. Graphene based technological developments are progressing along the right track towards a more sustainable world.”
The partners include the University of Cambridge, UK, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland, Empa-Swiss Federal Laboratories for Material Science and Technology, Switzerland and Graphene Flagship Associate Member the University of Exeter, UK, in collaboration with colleagues at CSIR-Advanced Materials and Processes Research Institute, India, National University of Singapore (NUS), A*STAR (Agency for Science, Technology and Research), Singapore, the University of Illinois and Argonne National Laboratory, US.
Dwivedi et al. “Graphene Overcoats for Ultra-High Storage Density Magnetic Media.” Nature Communications, 2021, 12, 2854, DOI: 10.1038/s41467-021-22687-y.