Data storage capacity is enhanced by mixing hard and soft magnetic materials

February 26, 2014
Data storage capacity is enhanced by mixing hard and soft magnetic materials
Combining grains of iron–platinum and titanium oxide creates a composite material with the ideal properties for magnetic data storage. Credit: Bastian Weltjen/iStock/Thinkstock

A computer hard disk uses a process called magnetic recording to store digital data. This involves applying a small field to switch the physical properties of grains of a magnetic material. The grains exist in one of two possible states, which represent the '1's and '0's of binary information.

Now, Tie-Jun Zhou and co‐workers at the A*STAR Data Storage Institute in Singapore show that a combination of two can reduce the size of these grains while maintaining the ideal for magnetic recording1. Smaller grains allow information to be stored at higher densities, enabling the fabrication of disks with much larger storage capacities.

The iron–platinum (FePt) alloy is a common choice for magnetic storage as it has several beneficial properties: it forms grains that are just a few tens of nanometers wide, and it maintains its magnetic state even when heated because of a large protective 'energy barrier'. But FePt has a notable drawback—to switch its state, FePt requires a much larger than those produced by conventional hard drives. These characteristics make FePt a 'hard' magnetic material.

To tackle this high-field problem, Zhou and his team combined FePt with a 'soft' magnetic material—a material that is relatively easy to magnetize by applying only a small magnetic field. "Exchange-coupled composite materials can reduce the energy required for writing," explains Zhou. The important question, however, is whether the composite material still has the beneficial energy barrier of FePt.

Zhou and co-workers measured the energy barrier in thin films of FePt and titanium oxide. They observed that exchange coupling has little effect on the energy barrier, but that the energy barrier decreases as the soft-layer thickness increases.

Previous studies have measured the of exchange-coupled composites by applying the switching magnetic field in a direction perpendicular to the thin films. In contrast, Zhou and the team used an alternative approach that applies the field at an angle of 45 degrees. They found that this method gives a more accurate result—the conventional approach could produce overestimates by as much as 70 per cent.

"Such an error leads to an overestimation of the lifetime of recording by several orders of magnitude," says Zhou. "So these results should prevent future mistakes in predicted lifetime that might have led to data loss in hard disks." Gains could also be made by optimizing the soft-layer thickness and the interlayer exchange-coupling strength.

Explore further: Reducing information stored in magnetic thin films to the size of single grains could improve computer hard drives

More information: Zhou, T.-J., Cher, K. M., Lwin, P. W. & Hu, J. F. "Energy barrier measurement and optimization in exchange coupled FePt/TiO2 nano-composite thin films." Journal of Magnetism and Magnetic Materials 331, 187–192 (2013). DOI: 10.1016/j.jmmm.2012.11.044

Related Stories

Controlling magnetism with an electric field

February 18, 2014

There is a big effort in industry to produce electrical devices with more and faster memory and logic. Magnetic memory elements, such as in a hard drive, and in the future in what is called MRAM (magnetic random access memory), ...

Recommended for you

'Material universe' yields surprising new particle

November 25, 2015

An international team of researchers has predicted the existence of a new type of particle called the type-II Weyl fermion in metallic materials. When subjected to a magnetic field, the materials containing the particle act ...

CERN collides heavy nuclei at new record high energy

November 25, 2015

The world's most powerful accelerator, the 27 km long Large Hadron Collider (LHC) operating at CERN in Geneva established collisions between lead nuclei, this morning, at the highest energies ever. The LHC has been colliding ...

Exploring the physics of a chocolate fountain

November 24, 2015

A mathematics student has worked out the secrets of how chocolate behaves in a chocolate fountain, answering the age-old question of why the falling 'curtain' of chocolate surprisingly pulls inwards rather than going straight ...


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.