The storage capacity of hard drives is increasing explosively, but the speed with which all that data can be written has reached its limits. Researchers at Eindhoven University of Technology (TU/e) and the FOM Foundation present a promising new technology which potentially allows data to be stored 1,000 times as fast in Nature Communications on 10 July. The technology, in which ultra-short laser pulses generate a ‘spin current’, also opens the way to future optical computer chips.



A hard drive stores bits in the form of tiny magnetic domains. The directions of the magnetic north and south poles of these domains, which are referred to as the magnetization, determine whether they are a 0 or a 1. Data is stored by changing the direction of the magnetization 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.



Limit reached

The stronger the local magnetic field, the faster the switch takes place. But this is subject to a limit which has now almost been reached. “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 TU/e researcher Sjors Schellekens. He is the lead author of a publication in Nature Communications, in which together with colleagues he presents a new technology.



Magnetic stream

The physicists, led by TU/e professor prof.dr. Bert Koopmans, 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 which all have the same spin. The resulting ‘spin current’ changes the magnetic properties of the material (see the figure for an explanation of the technology).