Nanoantennaes and magnets and light

Ultrafast energy-efficient magnetic memory goes brain-like


Researchers at the Department of Physics in a collaboration with Uppsala University and Radboud University (The Netherlands) have checked another box in the search for the ultimate magnetic memory - one that will be extremely fast, energy efficient and run on light. Their latest results show that using special antennas for light would decrease the power needed to operate such a memory to at least three times less than previously believed, and that the memory might even inhabit a brain-like function.

“We used optical nanoantennas to channel light onto nanoscale magnets, and observed how the light influenced their magnetic state. One amazing feature we discovered is that we can tune that magnetic state any way we want”, says Alexandre Dmitriev, professor at the Department of Physics.

Nano Letters cover

This how it's done: The researchers take nano-sized TbCo rare-earth transition-metal alloy magnets, position them right above the nano-sized optical antennas that concentrate light into the magnets, and pack the antennas into square grids. When femtosecond light-pulses hit the grids, the nanomagnets are demagnetized – a first, critical step towards realizing a magnetic memory that could be switched at just a few femtoseconds (i.e., 10 000 times faster than the regular magnetic bits are operated).

Three times less energy

The findings demonstrate that the light-power needed to demagnetize such nanomagnets is actually three times less than what was previously thought to be the case. This means that the nano-antennas truly do focus light onto the magnets and help them perform their function.

"The surprising part is that since the antennas are packed into grids, light is not only concentrated on individual nanomagnets, but can be diverted from them when it couples to the entire grid, forming so-called lattice resonances that are related to light diffraction on periodic structures," says Alexandre Dmitriev.

This allows the researchers to actually choose what magnetization

state the nanomagnets will adopt, so it’s not only ‘1’ or ‘0’ for a magnetic bit, but many values in-between. Since these are magnets, they keep the ‘memory’ of those values for some short time, somewhat similarly to how our human brain processes information. As a possible result, so-called neuromorphic computing might become possible to operate extremely fast by using light and nanomagnets.

The quest to create better data storage

“As the need for data storage is growing every day, so is the energy needed to operate all that ever-growing storage. We must bring this energy cost down as much as we can in order to live sustainably. In addition, alternative way of processing information, taking inspiration from nature and the human brain, will help us to make information processing way more energy-efficient - and much faster," says Alexandre Dmitriev.

The work has recently been published as a cover story in research journal Nano Letters. The project is the result of a collaboration between University of Gothenburg, Uppsala University and Radboud University (The Netherlands).

Read the full scientific article here