Contrôler l’électronique par photoexcitation – Le magnétite ouvrira-t-il la voie aux appareils de prochaine génération ?

Le potentiel du spintronique

Electronic components like transistors are traditionally built out of silicon and rely on semiconductors. The 0 and 1 signals in binary indicate the passing or blocking of an electric current. An alternative way to perform computation is spintronics devices that run on the spin of electrons (a fundamental quantum characteristic) rather than electric current (flow of electrons).

Le spintronique présente quelques avantages par rapport aux systèmes électroniques classiques, notably:

• Des données plus rapides, car le spin peut être modifié beaucoup plus rapidement.
• Une consommation d’énergie moindre, car le spin peut être modifié avec moins de puissance que celle nécessaire pour maintenir un flux d’électrons afin de créer un courant.
• Des métaux simples peuvent être utilisés à la place de matériaux semi-conducteurs complexes.

Spintronics is notably used for hard drives and has allowed storage capacity to grow over the last decade.

A material already used in spintronics is magnetite, a naturally occurring mineral made of oxygen and two forms of iron at different levels of oxidation.

Source: Britannica

Bien que le magnétite soit connu pour ses propriétés magnétiques depuis des décennies, il semble qu’il reste encore beaucoup à apprendre à son sujet.

Researchers from the EPFL in Switzerland have discovered that lasers can create new phase changes in magnetite that were previously unknown. This could, in turn, lead to a new generation of electronic equipment.

Les propriétés cachées du magnétite

The researchers focused on magnetite due to its metal-to-insulator properties, allowing it to switch from a conductor of electricity to blocking it. This is also known as a phase transition, where the properties of a material suddenly change from one stage to another, a little like how liquid water can turn into ice, with very different properties.

By using two different types of lasers, one emitting light at 800nm and one at 400nm (infrared and visible light), they discovered that new phases appeared in magnetite that had not been identified until now.

This is not a trivial matter, as the researchers had to detect change happening in an infinitesimally small period of time. To do so, they used a technique called Diffraction électronique ultrarapide (UED), which allowed them to look at atom movements lasting less than a picosecond or a trillionth of a second.

Modification de la configuration spatiale

Normally, magnetite’s atomic structure is “a monoclinic lattice,” where the unit cell is shaped like a skewed box with three unequal edges. Two of its angles are 90 degrees, while the third is different.

Source: ACS

The 800nm light causes the magnetite atomic structure to compress, turning it into a cubic structure. The ultra-rapid observation showed the researchers that it happened through a 3-stage process.

The 400nm instead caused the metal atomic structure to expand, creating a very stable configuration, making it a very stable insulator.

This configuration is different from the previously known stable equilibrium of magnetite and provides deep insight into what is actually happening during the metal-to-insulator transition.

Nouveaux systèmes électroniques

This discovery means that it is possible to change the effect on spin and current of magnetite just with light from lasers.

Thanks to very quick laser systems, it could allow for photon pulse to quickly change in a controlled fashion the nature of the metallic material.

“Our study breaks ground for a novel approach to control matter at ultrafast timescale using tailored photon pulses.

Being able to induce and control hidden phases in magnetite could have significant implications for the development of advanced materials and devices.

For instance, materials that can switch between different electronic states quickly and efficiently could be used in next‑generation computing and memory devices.”

Mémoire améliorée

Spintronics and magnetite are new frontiers for electronic system manufacturers. What started in a hard drive is now expanding to other memory systems.

For example, random access memory (DRAM) could be replaced with magnetic RAM (MRAM). The first version of this concept is an already commercialized product by Everspin and has been used in Airbus aircraft, thanks to its resistance to temperature changes as well as cosmic radiation compared to traditional memory systems.

Another advantage of MRAM is its smaller size and lower power consumption, which means up to 80% less power demand . This can allow MRAM to be incorporated as cache memory in processors at a greater total capacity while consuming less power and generating less heat , with both space and heat becoming key limiting factors in processor improvement.

Photonique ?

The use of laser in changing magnetite conditions is reminiscent of the growing field of photonics, one of the options we discussed dans notre article sur les entreprises qui déplacent le calcul au‑delà des systèmes à semi‑conducteurs.

A system already using laser and light to perform computation could greatly benefit from a memory system that relies on magnetite’s phase change induced by light. This could potentially allow the computation result to be directly converted into data with little intermediary step-consuming power and slowing things down.

Entreprises de spintronique

1. Everspin Technologies

Everspin est la branche de Freescale (actuellement nommée NXP, symbole boursier NXPI) dédiée au développement de systèmes de mémoire MRAM. Elle a été scindée et introduite en bourse en 2016.

Everspin est considérée comme le leader de la technologie MRAM, héritant de l’expérience de Freescale qui a été le premier à commercialiser une puce MRAM en 2006.

Because MRAM is a memory that persists even in the absence of a current, it is increasingly used in sensitive use cases where critical data are important.

Portée par des applications omniprésentes telles que l’analyse de données, l’informatique en nuage, tant terrestre qu’extraterrestre, l’intelligence artificielle (IA) et l’Edge AI incluant l’Internet des objets industriel, le marché de la mémoire persistante devrait croître à un TCAC de 27,5 % entre 2020 et 2030

Everspin

Source: Everspin

The company estimates the market will reach a $7.4B size by 2027. The company has no debt and positive free cash flow since 2021.

Everspin MRAM products are currently occupying a small but growing niche, serving markets where reliability is crucial like aerospace, satellites, data recorders, patient monitoring devices, etc.

Source: Everspin

The growth of chipsets, AI, and synaptic systems might also be a long-term boost for the company.

2. NVE Corporation

Another leader of spintronics, NVE has been working on this technology since its first patent in MRAM technology in 1995.

It produces des capteurs spintroniques et des isolateurs, mostly used in measurement and sensor systems for cars, gears, medical devices, power supplies, and other industrial devices.

Source: NVE

This puts NVE in a somewhat different category than Everspin, with NVE more of an industrial company with a strong position in a niche market (magnetometer using spintronics), while Everspin is more of a memory/computing company working with and in competition with the like of Intel (INTC ), Qualcomm (QCOM ), Toshiba, and Samsung also developing their own MRAM product.

It can make it a more (or less) attractive stock depending on investors’ profile, with NVE’s stock more likely to appeal to more conservative investors looking for some dividend yield and safety.