Styring af elektronik gennem fotoexcitation – Vil magnetit bane vejen for næste generations enheder?

Potentialet for spintronik

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).

Spintronik har nogle fordele i forhold til klassiske elektroniske systemer, notably:

• Hurtigere data, da spin kan ændres meget hurtigere.
• Lavere energiforbrug, da spin kan ændres med mindre kraft end det kræver at opretholde en strøm af elektroner for at skabe en strøm.
• Simple metaller kan bruges i stedet for komplekse halvledermaterialer.

Spintronik er især brugt i harddiske og har gjort det muligt for lagerkapaciteten at vokse i løbet af det sidste årti.

Et materiale, der allerede anvendes i spintronik, er magnetit, et naturligt forekommende mineral bestående af oxygen og to former for jern i forskellige oxidationsniveauer.

Kilde: Britannica

Selvom magnetit har været kendt for sine magnetiske egenskaber i årtier, er der tilsyneladende stadig mere, der kan læres om det.

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.

De skjulte egenskaber ved magnetit

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 Ultrafast Electron Diffraction (UED), which allowed them to look at atom movements lasting less than a picosecond or a trillionth of a second.

Ændring af rumlig konfiguration

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.

Kilde: 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.

Nye elektroniske systemer

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.”

Bedre hukommelse

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.

Fotonik?

The use of laser in changing magnetite conditions is reminiscent of the growing field of photonics, one of the options we discussed i vores artikel om virksomheder, der flytter beregning ud over halvleder-systemer.

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.

Spintronik-virksomheder

1. Everspin Technologies

Everspin is the branch of Freescale (currently named NXP, stock ticker NXPI) that is dedicated to developing MRAM memory systems. It got spinned-out and IPOed in 2016.

Everspin is considered the leader of MRAM technology, inheriting Freescale’s experience of being den første til at kommercialisere en MRAM-chip i 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.

Driven by pervasive applications such as data analytics, cloud computing, both terrestrial and extraterrestrial, artificial intelligence (AI), and Edge AI including Industrial IoT, the market for persistent memory is projected to grow at a CAGR of 27.5% between 2020 and 2030

Everspin

Kilde: 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.

Kilde: 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 har arbejdet med denne teknologi siden deres første patent på MRAM-teknologi i 1995.

It produces spintronic sensorer and isolatorer, mostly used in measurement and sensor systems for cars, gears, medical devices, power supplies, and other industrial devices.

Kilde: 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.