“By changing the polarisation of the laser pulse we deterministically steer the net magnetisation in the garnet: we write 0 and 1 magnetic bits at will,” physicist Alexey Kimel from Radboud University explains.
“This mechanism outperforms existing alternatives, allowing the fastest ever magnetic write-read recording event, lower than 20ps, accompanied by unprecedentedly low heat load.”
The problem with the researchers’ initial findings was that the mechanism of the recording relied on laser-induced heating that reached temperatures above which the magnetic order is destroyed.
In order to tackle the heating problem, low optical absorption is necessary, which means a dielectric material needs to be used. For this study the scientists chose yttrium iron garnet (YIG). It is impossible to record information through light on normal YIG. But to increase its sensitivity to optical excitation, the scientists doped it with cobalt ions.
The scientists found that in the cobalt substituted garnet film, a single linearly polarised femtosecond laser pulse promotes switching of spins between different states.
Using light for magnetic switching on garnet films will probably not be applied in personal computers. “The technology gap between storing on metal and garnet crystal is too big,” Alexey Kimel thinks.
“But it could be an interesting option for the big data warehouses of Google and Facebook and the like. Another possible use could be data recording at low temperatures. Super conducting electronics and quantum computers lack a fast memory system that can record at temperatures below -263°C.”
