Magnetic Recording

Magnetic Recording Assisted by Heat Promises to Achieve Record Storage Densities

Hard drives soon will be able to hold up to 1 Tb of data per sq. inch. Storage maker Seagate has introduced new magnetic recording technology called Heat-Assisted Recording which will allow manufacturer to increase disk capacities up to 10 Tb and higher; 1 Tb (terabit) equals 1,000 Gigabits. Heat-Assisted Magnetic Recording (HAMR) approach is going to double the storage density of today's best hard drives and it looks like Seagate will be the first storage maker to reach and cross the 1 terabit per square inch benchmark.The same technology promises to deliver extraordinary capacities of up to 60 Tb within next ten years with theoretical storage densities reaching 10 Tb per sq. inch - long way from today's 750 GB per square inch area density. That, and the new generation of data compression algorithms could bring us to the next level of capacities we never dreamed of.


The rise of Internet, online search and cloud computing continues to demand for greater storage capacities in our data-hungry age. One of Seagate executives Mark Re admits that advances in magnetic recording fields such as HAMR will become strong influences in upcoming future able to support ever increasing demand for more space. There are only few known ways to increase areal density - by packing more bits of data per linear inch of track and by placing tracks closer to each other. Hard drive manufacturers have been able to double disk capacities almost every couple years. Today, Seagate has achieved the linear density of 2 megabits per inch, or 1 terabit per square inch, which is more than double the current capacities. The first generation of HAMR drives will boast up to 6 TB volumes on 3.5 inch drives and 2 TB for 2.5 inch drives for portable electronics.

The heat-assisted magnetic recording uses laser to heat up the tracks of a disk currently targeted by the read-write head, allowing those regions to be made narrower and placed closer to each other. Seagate says the method promises to keep increasing storage density, which indeed could lead to 60 terabyte hard drives closer to the end of this decade. The HAMR is building up on top of existing Perpendicular Magnetic Recording (PMR) approach where the read-write head lines up individual bits vertically, which is perpendicular to the direction of tracks. This way polarized particles take less space, are placed closer to each other and therefore lead to narrower tracks, which in turn produce significantly higher density.

In previous generation of Longitudinal Recording the bits were inefficiently stretched all the way across or along the tracks taking unreasonable amount of space. Longitudinal Recording technology was replaced by the PRM in mid-2000 which led to great deal of storage capacity increase since then. Today's hard disk platters are coated with very thin cobalt-platinum alloy layer. Each bit is forced by magnetic field of a writing head into 1 or 0 vertical position where it remains until repositioned again. The closer bits are placed towards each other, the higher the density of the disk. When the recorded areas become as small as 25 nm, bits become unstable and vulnerable to heat and to other influences. There are more stable alloys available today, such as iron-platinum, but they demand stronger magnetic fields to change the position of the bit, unless the area is heated up prior to applying the magnetic field. That is what heat-assisted recording does, by warming up iron-platinum coating with a short laser pulse right ahead of the magnetic head. Reading does not involve heat up and therefore is less heat intense.

There are couple obstacles to overcome however before Seagate will have a commercial product. The biggest one is that conventional lens optics are not capable to focus light on 25 nm tracks, therefore Seagate is developing a parabolic mirror able to squeeze light down to a quarter of its wavelength. A miniature gold mirror catches light and bounces it back at a 30 nm wide track. The iron-platinum alloy also demands more attention than conventional coating - it has to be smoother, with very good quality granular structure. The multi-layer surface must be crystallized in order to provide right linear heat distribution on the surface of a platter. Seagate has proven that they were able to overcome all these issues during the demo test.This is very exciting news, representative says!

References: Seagate, Newsy, Megan Murphy.