Global Sources
EE Times-Asia
Stay in touch with EE Times Asia
EE Times-Asia > Memory/Storage

Magnetic materials squeeze more data on hard drives

Posted: 21 Jun 2013 ?? ?Print Version ?Bookmark and Share

Keywords:hard drive? heat-assisted magnetic recording? ferromagnetic material?

A team of researchers at the A*STAR Data Storage Institute in Singapore has developed a 'sandwich' of three iron alloy layers that according to them could help create computer hard drives that can store more data than ever before. Tiejun Zhou and co-workers said their findings, based on a technology called heat-assisted magnetic recording (HAMR), could boost the capacity of disks.

Conventional hard drives contain a tiny electromagneta write headthat hovers over a spinning disc coated with a ferromagnetic material. The electromagnet induces the magnetic field within small regions of the disc to point either up or down, encoding one bit of data.

Heat can jumble these magnetic bits and destroy the data. The latest disks use materials with a very large coercivitya measure of how difficult they are to demagnetise. However, write heads must exert even greater magnetic fields to encode data in such materials. The balance between bit size, coercivity and the electromagnet's strength ultimately puts an upper limit on disc density of about 1Tb per square inch.

In HAMR systems, each recording region is briefly heated above its Curie temperature, a point when magnetic coercivity drops significantly and a much smaller field can write the bit. Once the region cools, the coercivity rises and the bit locks into place.

Zhou's team found a way to reduce both the writing temperature and the switching field in HAMR systems. The upper ironCplatinum layer of the sandwich stores data bits. The lower iron-cobalt layer helps to channel the write-head's magnetic field, enabling data writing; and the middle ironCrhodium layer acts as a switch between the two. The middle layer is antiferromagnetic at room temperature so blocks any magnetic coupling between the other layers. At about 350K, however, it becomes ferromagnetic, allowing the layers to couple.

IronCplatinum normally has a Curie temperature of about 750K, but that plummets when coupled to the iron-cobalt layer. Data can therefore be written to the iron-platinum layer once the iron-rhodium layer becomes ferromagnetic, at about 350K.

Coupling also reduces the coercivity of the iron-platinum layer, so a write head would need only to generate one-third of the usual magnetic field to encode a bit. "Theoretically, the bit can occupy a space as small as 100 square nanometers," noted Zhou. The team now plans to reduce the size of the nanocrystals in each data region of the iron-platinum layer, while maintaining its high coercivity.

Article Comments - Magnetic materials squeeze more data...
*? You can enter [0] more charecters.
*Verify code:


Visit Asia Webinars to learn about the latest in technology and get practical design tips.

Back to Top