Using Lasers to Magnetize Non-Magnetic Substances May Transform Modern Computers

Quantum computing possesses huge potential. It could completely transform industries and change the way we understand the universe. By combining the principles of quantum mechanics with computer science, quantum computing allows for complex problems to be solved with ease by processing huge amounts of data in parallel to exploring multiple solutions. 

This way, quantum computers can help in drug discovery, climate modeling, enhancing AI capabilities, and solving optimization problems. They also have potential in cybersecurity by breaking existing encryption methods and creating unbreakable quantum encryption systems.

Over the years, we have made significant progress in quantum computing, including quantum supremacy, error correction codes, and cloud-based quantum computers. However, this progress has been largely limited to the extremely cold temperatures of laboratories, which may be about to change. 

Now, researchers at the Nordic Institute for Theoretical Physics (NORDITA), a collaboration between the five Nordic countries, Stockholm University and the Ca’ Foscari University of Venice, have successfully demonstrated quantum behavior at room temperature by utilizing laser light. For the first time, laser light was able to make non-magnetic materials magnetic.

It is of utmost importance because magnetism plays a key role in how a computer functions. Computer memory uses small-scale electromagnets magnetized with voltage to enable the binary states of “on” or “off.” The way atoms and electrons react to magnetic fields allows electronic devices to read, write, and manipulate data.

In this new study, researchers showed just how exposing a non-magnetic material to high-frequency laser radiation can produce a magnetic effect at room temperature.

The new breakthrough has the potential to pave the way for more energy-efficient and faster computers, information transfer, and data storage. It shows incredible promise in revolutionizing electronics, particularly those machines built using quantum technology, which tend to operate at temperatures around absolute zero (-273 degrees Celsius).

Turning Non-Magnetic Materials Magnetic

In the latest study, the researchers used strontium titanate (SrTiO₃), an oxide of highly chemically reactive strontium (Sr) and lightweight titanium (Ti). At the human habitable temperature, it has a perovskite structure and is known for its high dielectric constant.

This material was subjected to light from a high-frequency laser, which stirred up the atoms and mobilized them. This generated electrical currents within strontium titanate, making it magnetic.

Talking about the novelty of their method, the study’s lead author Stefano Bonetti, a physicist at Stockholm University, and Ca’ Foscari said it was:

“In the concept of letting light move atoms and electrons in this material in a circular motion, so to generate currents that make it as magnetic as a refrigerator magnet.”

Turning non-magnetic material magnetic isn’t anything new, though. It has been previously predicted and looked into. 

Back in 2015, Nature published research that discovered that copper and manganese, two common non-magnetic metals, can be turned into magnets by combining thin films of the metals with carbon-based organic molecules. While the results were obtained at room temperature, the magnetism was weak and faded away after a few days.

This experiment was based on a 1930s theory by theoretical physicist Edmund Stoner from the University of Leed, who investigated what makes it possible for an element to be magnetic.

In 2020, a research team was also able to modify non-magnetic oxide materials and make them magnetic through controlled layer-by-layer growth of each material. The same year, another team of researchers used electricity to switch on magnetism in the non-magnetic pyrite or iron sulfide. The technique used in this study was electrolyte gating, which involved having pyrite in contact with an electrolyte (ionic liquid) and then applying one volt of electricity that moved positively charged molecules and created a measurable magnetic force. In this case, switching off the voltage shut down the magnetism as well.

Using light to alter a material’s properties has also been gaining considerable scientific attention for some time now. 

The thing is, magnets and the magnetic field are usually generated by circulating currents. In 2019, physicists illuminated non-magnetic metallic disks with linearly polarized light, circulating electric currents and having magnetism emerge spontaneously in the disk. In principle, this method can turn non-ferrous metals into magnets “on-demand” using laser light.

Using Light to Rotate Atoms & Generate Current

Magnetization that is caused by rotation on a macroscopic scale is known as the Barnett effect. Under this effect, a material is rotated entirely to align the inherent angular rotations of disarranged magnetic material’s electrons to generate a net magnetic field inside it.

In the new experiment, rotation on the atomic scale was made in non-magnetic materials by relying on circularly polarized laser pulses. The pulses rotated the atoms in the material to yield collective chiral phonons, which are circularly polarized vibrations that are resonant with the frequency of the laser.

For this, a new light source was developed in the far-infrared (FIR), which is circularly polarized, meaning it has a ‘corkscrew’ shape. When laser light with this kind of polarization enters a material, the circular polarization is then transferred to its atoms by rotating them and producing atomic currents. If the light’s frequency matches that of the atom’s vibration, the effect is amplified, and as a result, quite a large magnetism is produced. 

So, the experiment that was carried out by the international group led by Bonetti then subjected the quantum material strontium titanate (SrTiO3) to intense but short laser beams of a peculiar wavelength and polarization to induce magnetism. The 800-nm, picosecond-long pulses were shot from a 100-µm far-infrared laser. 

In particular, the Kerr rotation of the probe pulses was measured. The team also used diverse temperatures, ranging from 160 to 360 Kelvin. This showed that the highest response was achieved at 280 K (7°C). At this point, the pulses’ terahertz electric field was resonant with the material’s first optical phonon mode.

In this latest study published in Nature, the lead author Bonetti noted that it was the first time they were able to induce and see how the material actually becomes magnetic at room temperature clearly. 

This approach further allowed the team “to make magnetic materials out of many insulators, when magnets are typically made of metals,” he added.

Meanwhile, the degree of magnetization induced via the laser technique was measured using an established effect in which light reflects off a material differently depending on its magnetism.

In their experiment, the measurements showed that the material had become magnetic. However, the magnitude of induced magnetization based on known theoretical methods for calculating this quantity has been about four orders of magnitude greater than expected. This difference was ascribed to oversimplifications made by the physicists in their calculations. 

Another group of researchers used circularly polarized infrared laser pulses to temporarily induce a magnetic effect in a non-magnetic material. 

Scientists from Radboud University, Netherlands, in collaboration with Nihon University, Japan, did this, but instead of conventional broadband pulses, they used very narrow-band pulses from the FELIX free-electron lasers, which enabled them to better target particular lattice vibrations at resonance. They further used the created magnetization to switch a magnetic alloy’s magnetization.

According to these researchers, phononic resonance could be used as a new and fast way to write data to magnetic media. Changing the circularly polarized light’s rotation direction also allowed the team to change the direction of magnetization.

The Growing Use of Laser Light

The use of laser light is growing rapidly. Just this week, scientists made a new discovery: A concentrated laser beam can change a solid material’s magnetic state, showcasing huge potential in ultrafast computing memory.

For this, the scientists prepared a new “elemental” equation that describes the link between the frequency and amplitude of light’s magnetic field and the energy absorption properties of a magnetic material. According to Amir Capua, a physics professor at the Hebrew University of Jerusalem:

“It lets us completely reconsider optical magnetic recording and navigate our way to a dense, energy-efficient, cost-efficient optical magnetic storage device that doesn’t even exist yet.” 

This tech is expected to lead to faster and more efficient MRAM components in the future. 

The global laser tech market size is actually projected to grow to $29.5 bln before the decade is over, up from the current $20 bln valuation. These numbers are due to the laser’s wide potential in various industries.

A laser is an optical device that produces a beam of light by stimulating the emission of radiation. Due to this light’s unique properties, such as high intensity, coherence, monochromaticity, and directionality, lasers are widely used in medicine, communications, science, the military, and more. As a result, many inventions and experiments have been happening in the laser space.

Most recently, scientists in Romania created the world’s most powerful laser emission, which is one-tenth the power the sun exudes and is received on Earth. Installed at a center near Bucharest, operated by the French company Thales, the laser is reported to have an output of 10 petawatts (10 quadrillion watts). The peak was achieved only for an extremely short period, about 25 femtoseconds, and across a width of just three micrometers.

The scientists hope the laser will lead to revolutionary advances across sectors ranging from health to space. This invention can be applied to treat nuclear waste and clean up space debris.

In another recent research, RIKEN physicists realized very short pulses of laser light that had a peak power of 6 trillion watts. This is as much as the power produced by 6,000 nuclear power plants. This achievement is to help develop attosecond lasers which can enable the study of electrons. 

Last year,  Anne L’Huillier, Pierre Agostini, and Ferenc Krausz were awarded the Nobel Prize in Physics for their research into attosecond (one quintillion of a second) pulses of light.

These ultra-short laser pulses can help light up extremely fast processes, providing scientists with a powerful way to capture and probe them. 

“By making it possible to capture the motion of electrons, attosecond lasers have made a major contribution to basic science.”

– Eiji Takahashi of the RIKEN Center for Advanced Photonics

They are expected to be used to diagnose medical conditions, observe biological cells, and develop new materials.

Click here to learn how lasers are set to play a pivotal role in the coming decades.

Future Potential of Laser-Induced Magnetism

Funded by an ERC Synergy Gran and the Knut and Alice Wallenberg Foundation, the study that turned non-magnetic materials magnetic at room temperature noted that in physics, a matter’s collective order is one of the most basic and fascinating occurrences and that dynamical multiferroicity has been introduced to describe the emergence of magnetization. 

“In simple terms, the coherent rotating motion of the ions in a crystal induces a magnetic moment along the axis of rotation,” it stated. 

Due to this very mechanism, the team was able to demonstrate magnetization in the archetypal paraelectric perovskite SrTiO3. These results have already been reproduced in several other labs.

However, the material’s magnetism was only maintained for about one trillionth of a second. It has not been long enough to find its application in computer memory.

Having said that, this is a great starting point where scientists have finally been able to bring theory to practicality. This certainly has important potential technological applications that’ll be realized over time with more research.

The experiment findings, as per the research, show a new path for magnetism control. This could be utilized for extremely fast magnetic switches, for instance, through coherent control of lattice vibrations using light.

Moreover, while this study has started off with strontium titanate, other more complex materials can be explored in the future that may be able to maintain their magnetism for longer periods of time. From here, the only way is forward with more exciting discoveries to be made that’ll open the door to use in computing devices.

As the study author Alexander Balatsky, professor of physics at NORDITA, stated: 

“This can be used for faster information transfer and considerably better data storage, and for computers that are significantly faster and more energy-efficient.”

So, while the results are promising and can lead to great improvements in electronics and computing that are based on magnetization, further work is needed.

Click here to learn about the current state of quantum computing.