Novel approach to fabrication of magnetic memory elements may lead to new generation of ultra-high-capacity hard drives

May 10, 2012 By Lee Swee Heng
A magnetic film patterned into an array of dots (background) is known as a bit-patterned medium, and can store data at very high areal densities. Each dot requires a slightly different magnetic field to write or erase. Ranjbar and co-workers reduced this variation by adding a continuous layer underneath the dots, made of the same material as the dots themselves (green). By comparison, the traditional approach (yellow) had both a wider variation, and higher average switching fields. Credit: A*STAR

Information in most computer memories is stored in the form of ‘bits’ represented by the polarization of tiny magnets on the surface of memory devices such as the computer’s hard drive. The capacities of these devices have increased exponentially over the last 30 years, a feat made possible by progressively reducing the area taken up by the magnets storing the information. In modern machines, these magnets are so small that reducing their size any further risks creating unstable data, due to random flipping of the direction of polarization of the magnets at higher densities. Now, Mojtaba Ranjbar and colleagues at the A*STAR Data Storage Institute have honed a key technology, called bit-patterned media, to overcome this problem and allow data to be stored at previously unattainable densities.

Bit-patterned media technology replaces the continuous magnetic film traditionally used in hard drives with an array of small, patterned magnetic dots (see image), each of which stores a bit of data. By carefully designing the size and shape of these dots, data can be stored at very high densities without the instability that would be encountered if a continuous film were used.

Using bit-patterned media, however, is not without its own difficulties, chief among which is a problem known as 'switching field distribution', whereby the magnetic field required to write or erase data in each dot differs slightly and by an unknown amount. As a result, the magnetic field applied by a write head may be too small, or too large, resulting in data errors.

Previous work by other researchers sought to minimize the switching field distribution problem by covering all of the magnetic dots with a continuous magnetic film placed on top of the dots, which alters the magnetic interactions between individual dots. The approach called 'capped bit-patterned media' traditionally requires different magnetic materials for the dots and film, introducing additional fabrication complexity.

Ranjbar and co-workers used the same material for the film and dots, and positioned the dots above the film rather than below it. This approach allowed a particularly simple fabrication process, in which dots were etched in a controlled fashion, leaving a continuous, unetched film underneath and obviating the need for a separate deposition step to introduce a new magnetic material.

The researchers found that this simplified process successfully reduced switching field distribution, and also lowered the field strengths necessary for writing data. Ranjbar comments, “Combined with the ease of fabrication, this technology should prove useful in bit-patterned media for next-generation hard disk drives.”

Explore further: New insights found in black hole collisions

More information: Ranjbar, M., et al. Anomalous Hall effect measurements on capped bit-patterned media. Applied Physics Letters 99, 142503 (2011).

add to favorites email to friend print save as pdf

Related Stories

Toshiba makes a breakthrough in hard-drive capacity

Aug 23, 2010

(PhysOrg.com) -- Last Wednesday Toshiba made an announcement at the Magnetic Recording Conference in San Diego that they have made a breakthrough in their research of bit-patterned media that would result ...

The art of magnetic writing

Aug 01, 2011

Computer files that allow us to watch videos, store pictures, and edit all kinds of media formats are nothing else but streams of "0" and "1" digital data, that is, bits and bytes. Modern computing technology is based on ...

Recommended for you

X-rays probe LHC for cause of short circuit

Mar 27, 2015

The LHC has now transitioned from powering tests to the machine checkout phase. This phase involves the full-scale tests of all systems in preparation for beam. Early last Saturday morning, during the ramp-down, ...

New insights found in black hole collisions

Mar 27, 2015

New research provides revelations about the most energetic event in the universe—the merging of two spinning, orbiting black holes into a much larger black hole.

Swimming algae offer insights into living fluid dynamics

Mar 27, 2015

None of us would be alive if sperm cells didn't know how to swim, or if the cilia in our lungs couldn't prevent fluid buildup. But we know very little about the dynamics of so-called "living fluids," those ...

Fluctuation X-ray scattering

Mar 26, 2015

In biology, materials science and the energy sciences, structural information provides important insights into the understanding of matter. The link between a structure and its properties can suggest new ...

Hydrodynamics approaches to granular matter

Mar 26, 2015

Sand, rocks, grains, salt or sugar are what physicists call granular media. A better understanding of granular media is important - particularly when mixed with water and air, as it forms the foundations of houses and off-shore ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.