Spintronics, what is it?
electrons are negatively charged elementary particles. They are part of the building blocks of atoms and form the electric current as they move. It is these negative charges that conventional microelectronic devices, such as the transistor, manipulate. Electrons also have another interesting property, called
spin is a quantum magnitude which has no classical equivalent, but which is comparable to one
the particle’s inherent magnetic moment, as if the electron were a small magnet rotating about itself. Just as a magnet has a north pole and a south pole, spin has one
orientation », Up (up) or down (down).
The whole art behind spintronics is therefore to utilize this degree of freedom to generate
new phenomena and seek to use them for improve performance electronic components and data storage. By manipulating the spin of the electrons rather than their charge, spintronics also promotes one electronics with very low power.
First steps in spintronics and first research conducted at CEA
spintronikor spin electronics, originated in the 1980s. It was born in 1991 at CEA, three years after the discovery of Albert Fert and Peter Grünberg of the so-called “giant magnetoresistance” phenomenon, which gave them the Nobel Prize in Physics in 2007. The principle: to vary the electrical resistance of a material consisting of successive magnetic (iron, cobalt, nickel, etc.) and non-magnetic (chrome, copper, silver …) by exposing it to an external magnetic field.
Experimental and theoretical research then began at CEA to use it in various units. From 1998, it was integrated into the reading heads on computer hard drives thanks to the work done by Bernard Diény, currently research director at CEA-Irig at the origins of the Spintec laboratory (see box), enabling a doubling of storage capacity each year.
Spintec, excellent laboratory
The Spintec laboratory was set up in 2002 by the CEA and CNRS in Grenoble with twelve researchers and contributed in particular to the emergence of MRAM memories. In 20 years, he has filed more than 80 patents and spun off four start-ups, three of which are still active: Crocus Technology, Hprobe and Antaios. Spintec now has about a hundred members.
The use of spintronics in MRAM memories
The use of spintronics is particularly illustrated in
non-volatile magnetic memory (MRAM)where it is used universally today.
Magnetic Random Access Memory is a non-volatile memory (retaining data without a power supply) that uses the spin of the electrons. There are various technologies for writing information in these memoirs, including the “spin transfer pair” studied in
Spintec Laboratory since 2004 and today present in our computers.
© The Challenges of CEA / J. Perrodeau
Download the infographic on MRAM memories, taken from Défis du CEA no. 249
Benefits of spintronics for MRAMs
- Non-volatility: the data is stored in the form of a magnetic orientation, that of the layers in the tunnel connections which remain in the absence of electric current;
write speed: up to 0.3 nanoseconds, ie. 1,000 to
100,000 times faster than flash memory;
- write perseverance: ferromagnetic materials allow more write-read cycles than memories involving atomic shifts (phase change materials or resistive oxides);
- Low voltage used: which makes it 400 times more energy efficient than a flash memory when writing.
Other uses of spintronics
Other digital devices use spintronics: magnetic field sensors, which are widely used in the automotive industry, robotics, biotechnology and biomedical sectors. The research will ultimately benefit other areas such as in-memory computing, cybersecurity, telecommunications, data centers and artificial intelligence.
USThis discipline, which has become significant, is part of the acceleration strategies of the France 2030 recovery plan.