New synthetic material for fast and cheap data storage

Scientists have developed a new synthetic material for optical data storage, an advance that brings the much cheaper method for storing data using light a step closer.
Optical data storage does not require expensive magnetic materials as synthetic alternatives work just as well, according to an international team from York, Berlin and Nijmegen.
When you store a file on your laptop or PC, the computer creates a code consisting of zeros and ones. These are actually tiny magnetic poles (spins) that can point in one of two directions: the 'zero' state or the 'one' state.
Switching these spins using a magnetic field is a relatively slow, energy-intensive process. An alternative is to switch them using light, which was first achieved by Radboud University Nijmegen in The Netherlands six years ago.

"Optical switching is only possible in special magnets, called ferrimagnets. However, these magnets are made of expensive rare earth metals, which are also difficult to produce at the nano-scale," said Professor Theo Rasing at Radboud University Nijmegen.
"Now, we have shown for the first time that it is also possible to switch synthetic ferrimagnets optically," said Rasing, who came up with the new synthetic material.

Other than with normal ferrimagnets, the production of synthetic ferrimagnets does not require the use of rare earth metals. This makes them cheaper and better for the environment, and therefore more suitable for use in computers.

Ferrimagnets have the unusual property that the spins are not all of the same magnitude.
"They are similar to anti-ferromagnets, in which the spins are found in pairs with opposite directions. However, because the magnetic poles have different magnitudes, ferrimagnets have a net magnetic moment," said Rasing.
This can be simulated by anti-ferromagnetically coupling thin layers of iron with a spacer layer.
"The iron is ferromagnetic - all the spins have the same magnitude and direction. It is therefore possible to create a net magnetic moment by combining two layers of different thicknesses and opposing magnetisation directions, for example," Rasing said.

"Coupling the spins works in a very similar manner, in the same two-step process that we previously developed for the normal ferrimagnets," he said.
When Rasing came up with his concept for the synthetic magnet, he contacted a group in York that could model the switching process.
"Their model showed that it really did work, and so we applied for a joint patent. It immediately became a hot topic, and there are already groups in San Diego, France and Germany working on actually producing and testing the synthetic ferrimagnets," he added.
The findings were published in the journal Applied Physics Letters.