Storing data a thousand times faster

Home Technologist Online Storing data a thousand times faster

New laser technology is set to boost the write speed of hard drives dramatically and pave the way for optical computer chips.

An artist’s impression of a laser pulse changing a magnetic bit.

The amount of data you can store on today’s hard drives seems endless compared with only a few years ago. Unfortunately, the same can’t be said for the speed with which you can write all those bits (binary digits) of data.

“The number of bits has been growing rapidly for many years, but the write speed has hardly increased. There’s a need for a new data storage technology,” says Sjors Schellekens from Eindhoven University of Technology (TU/e) in a press release. Today, Schellekens and colleagues unveiled a new technology that could enable data to be stored a thousand times faster than current limits allow.

A simplified representation of the new technology

A simplified representation of the new technology. Two magnetic layers, each with a different magnetisation, are separated by a neutral layer. A laser pulse strikes electrons in the upper layer. This causes them to move through the material, in the direction of the second layer. The spin of these electrons, in the direction of the magnetisation of the upper layer, exerts a force on the spin of the electrons in the lower layer to make them rotate in the same direction. This makes the magnetisation in the second layer change.

How does it all work?

A hard drive stores bits in the form of tiny magnetic domains. The directions of the magnetic north and south poles of these domains – the magnetisation – determine whether they are a 0 or a 1. Data is stored by changing the direction of the magnetisation of the associated bits.

At present this is done using a write head to create a local magnetic field, which makes a bit change direction. The stronger the local magnetic field, the faster the switch. But only up to a limit, which has now almost been reached.

To burst this limit, the physicists from TU/e use a special property of electrons, the spin – a kind of internal compass in the electron. Using ultra-fast laser pulses they generate a flow of electrons in a material that all have the same spin. The resulting ‘spin current’ changes the magnetic properties of the material.

“Unprecedented opportunities”

“The change in the magnetisation is of the order of 100 femtoseconds, which is a factor 1,000 faster than what is possible with today’s technology,” says Schellekens.

The team has also worked out the physical processes involved. “There was discussion among physicists about whether the generated spin current is actually able to cause the change in magnetisation. We now definitely show that this is really the case,” says Schellekens.

The next breakthrough the team is hoping to make is in optical computer chips. “Our technology allows optical data to be stored in the form of magnetic bits. That offers unprecedented opportunities if you want to use light as information carrier,” says Schellekens.

The technology is described in the July edition of Nature Communications.

by Lillian Sando


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