Tag Archives: magnetism

The Re-examination of Light and Magnetism: Nearly Two Centuries of Progress

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SEI 274892023

Illustration of Faraday’s experiment demonstrating the polarization of light by a magnetic field

Enrique Sahagun

In 1845, physicist Michael Faraday presented the first direct evidence linking electromagnetism and light. This connection has proven to be even more substantial than Faraday anticipated.

During his experiment, Faraday directed light through a glass containing a boric acid and lead oxide mixture placed within a magnetic field. He observed that this altered the light, resetting its polarization direction upon exiting the glass.

For the last 180 years, it has been widely accepted that light acts as an electromagnetic wave, with the “Faraday effect” illustrating how interactions between the magnetic field, charges in the glass, and the light’s electric component result in the rotation and alteration of the light waves as they enter the material.

Interestingly, it has long been assumed that the magnetic component of light has minimal involvement in the Faraday effect. However, Amir Capua and Benjamin Assulin, a research team from the Hebrew University in Jerusalem, Israel, has demonstrated otherwise.

“We now comprehend that the secondary component of light interacts with matter,” Capua states.

Capua explains that two main reasons deterred researchers from exploring the magnetic component of light’s involvement in the Faraday effect. First, magnetic forces within materials such as Faraday glass seem relatively weak compared to electrical forces. Second, when a material like Faraday glass is magnetized—aligning the quantum spins of its components with the magnetic field—these spins typically do not synchronize with the light wave’s magnetic component, indicating a weak interaction.

However, Capua and Assulin discovered that if the magnetic component of the light is circularly polarized (spiral-shaped), it may interact more strongly with the magnetic spins within the glass. They concluded that this is due to the magnetic component of light consisting of several corkscrew waves, even without deliberate manipulation.

Calculations by the two researchers revealed that if Faraday’s experiment were replicated using a magnetic material called terbium gallium garnet (TGG) instead of glass, this magnetic interaction could account for 17 percent of the Faraday effect when visible light passes through. Moreover, if infrared light were used with TGG, magnetic interactions might contribute up to 70 percent of the observed Faraday effect.

Igor Rozhansky, a researcher at the University of Manchester, UK, states that the new calculations are compelling and suggest promising experimental evaluations in the future. The previously overlooked magnetic component of the Faraday effect could provide researchers with innovative approaches to manipulate spin in materials, Rozhansky notes. He further mentioned that it remains an open question whether this effect may surpass the conventional Faraday effect in certain materials.

Future experiments could reveal discoveries extending from fundamental physics to practical applications. Capua envisions potential uses for the interaction between the magnetic spin of some materials and the magnetic component of light, which could lead to advancements in spin-based sensors and data storage technologies.

Science of the Renaissance: Italy

From Brunelleschi and Botticelli to polymaths like Leonardo da Vinci and Galileo Galilei, delve into the remarkable scientific minds and discoveries of the Renaissance that solidified Italy’s position at the forefront of scientific innovation.

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Source: www.newscientist.com

The Reinterpretation of Light and Magnetism: Two Centuries in the Making

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Illustration of Faraday’s Experiment Revealing the Polarization of Light by a Magnetic Field

Enrique Sahagun

In 1845, physicist Michael Faraday provided groundbreaking evidence connecting electromagnetism and light. This relationship has proven to be stronger than Faraday initially anticipated.

During his experiment, Faraday directed light through a mixture of boric acid and lead oxide contained in a magnetic field. He noticed a shift in the light, with its polarization direction being altered upon exiting the glass.

For the last 180 years, it has been a widely held belief that light acts as an electromagnetic wave, with the “Faraday effect” illustrating how the interplay of the magnetic field, the charge within the glass, and the electric component of light causes a rotation and deviation in the direction of light waves once they leave the material.

Surprisingly, scholars have long assumed that the magnetic aspect of light has little impact on the Faraday effect. However, Amir Capua and Benjamin Assulin from the Hebrew University in Jerusalem, Israel, have demonstrated otherwise.

“We now recognize that the secondary aspect of light interacts with matter,” explains Capua.

Capua notes two reasons why the magnetic component of light’s involvement in the Faraday effect has been overlooked. Firstly, the magnetic forces present in materials like Faraday glass seem significantly weaker compared to their electrical counterparts. Secondly, when a substance such as Faraday glass is magnetized, the quantum spins of its constituents behave like miniature magnets and often fail to synchronize with the magnetic component of the light wave, implying minimal interaction.

However, Capua and Assulin realized that if the magnetic component of light is circularly polarized (spiral or corkscrew-shaped), it may engage more effectively with the magnetic spins within the glass. They reached this conclusion based on the observation that light’s magnetic component naturally comprises several corkscrew waves without needing any specialized manipulation.

The researchers’ calculations indicate that repeating Faraday’s experiment using a magnetic material called terbium gallium garnet (TGG) in place of glass could account for 17 percent of the Faraday effect noted when visible light travels through it. When infrared light traverses the TGG material, magnetic interactions could explain as much as 70 percent of the resulting Faraday effect.

Igor Rozhansky from the University of Manchester, UK, asserts that these new calculations are compelling and point towards feasible experimental inquiries. The previously overlooked magnetic component of the Faraday effect could unveil new methods for controlling spin within materials, according to Rozhansky. He suggested it remains an open question whether this effect might surpass the traditional Faraday effect in certain materials.

Future experiments may yield groundbreaking findings, spanning from fundamental physics to practical applications. Capua envisions the possibility of utilizing the interaction between the magnetic spin of select materials and the magnetic component of light to manipulate materials, potentially leading to innovative spin-based sensors and data storage systems.

Science of the Renaissance: Italy

Explore the great scientific minds and breakthroughs of the Renaissance, from Brunelleschi and Botticelli to polymaths like Leonardo da Vinci and Galileo Galilei, and discover Italy’s pivotal role in shaping scientific inquiry.

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Source: www.newscientist.com

First-ever imaging of a novel form of magnetism: alternating current magnetism

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Alternating current magnetism is a unique form of magnetic ordering in which small magnetic components align antiparallel to their neighbors, but the structure housing each element is rotated relative to its neighbors. . Professor Peter Wadleigh and colleagues at the University of Nottingham have shown that this new type of magnetism exists and can be controlled with microscopic equipment.

Mapping of alternating current magnetic order vectors in MnTe. Image credit: Amin others., doi: 10.1038/s41586-024-08234-x.

Magnetic materials are used in a large portion of long-term computer memory and in the latest generation of microelectronic devices.

Not only is this a large and important industry, but it is also a global source of carbon emissions.

Replacing key components with alternative magnetic materials has the potential to lead to significant increases in speed and efficiency, while significantly reducing dependence on rare and toxic heavy elements required by traditional ferromagnetic technology .

Alternating magnets combine the advantageous properties of ferromagnets and antiferromagnets in a single material.

They are more robust, more energy efficient, and have the potential to increase the speed of microelectronic components and digital memory by a factor of 1,000.

“An alternating current magnet consists of magnetic moments pointing antiparallel to neighboring magnets,” Professor Wadley says.

“But each part of the crystal that hosts these tiny moments is rotated relative to its neighboring parts. It's like a twist on antiferromagnetism. But this subtle difference It has a big impact.”

Dr Oliver Amin, from the University of Nottingham, said: “Our experimental work provides a bridge between theoretical concepts and real-world implementation, and illuminates the path towards the development of alternative magnetic materials for practical application. I look forward to that.”

The new experimental study was conducted at the MAX IV international facility in Sweden.

This facility, which looks like a giant metal donut, is an electron accelerator called a synchrotron that generates X-rays.

A magnetic material is irradiated with X-rays, and the electrons emitted from the surface are detected using a special microscope.

This allows us to generate images of magnetism within materials with small feature resolution down to the nanoscale.

“Being the first to confirm the effects and properties of this promising new class of magnetic materials has been a hugely rewarding and rewarding privilege,” said the University of Nottingham PhD. Student Alfred Dal Din.

team's work Published in a magazine nature.

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OJ Amin others. 2024. Nanoscale imaging and control of alternating current magnetism in MnTe. nature 636, 348-353;doi: 10.1038/s41586-024-08234-x

Source: www.sci.news

Confirmation of the existence of a new form of magnetism

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AC magnetism works differently than standard magnetism

Libor Chemeikal and Anna Birk Hellenes

A new type of magnetism has been measured for the first time. Alternative magnets that combine the properties of different types of existing magnets could be used to make high-capacity, high-speed memory devices and new types of magnetic computers.

Until the 20th century, permanent magnets were thought to consist of only one type of ferromagnetic material. Ferromagnetic effects are seen in objects with relatively strong external magnetic fields, such as refrigerator magnets and compass needles.

These fields are caused by the magnetic spins of the magnet’s electrons aligned in one direction.

But in the 1930s, French physicist Louis Niel discovered another type of magnetism called antiferromagnetism, in which the spin of the electrons alternates up and down. Although antiferromagnets do not have the external magnetic field of ferromagnets, they exhibit interesting internal magnetic properties because of their alternating spins.

And in 2019, researchers Complex currents in the crystal structure of certain antiferromagnets, called the anomalous Hall effect, which could not be explained using the conventional alternating spin theory. Current flowed without an external magnetic field.

When we looked at the crystal from the perspective of a sheet of spins, it seemed to us that: A third type of permanent magnetism, called vicarious magnetism, may be responsible. Alternating magnets look like antiferromagnets, but the sheets of spin look the same no matter what angle they are rotated from. This explains the Hall effect, but no one had seen the electronic signature of the structure itself, so scientists weren’t sure if it was definitely a new kind of magnetism.

now, Juraj Krempaski and his colleagues at the Paul Scherrer Institute in Billigen, Switzerland, and his colleagues have discovered that by measuring the electronic structure within the crystals of magnesium telluride, previously thought to be antiferromagnetic, they were able to create an alternating magnet. confirmed the existence of

To do this, they measured how light reflected off magnesium telluride and found the energy and speed of the electrons in the crystal. After mapping these electrons, they found that they matched almost exactly the predictions given by simulations of alternating current magnetic materials.

The electrons appear to be split into two groups, which allows them to move more within the crystal and is the source of the unusual magnetic properties. “This gave us direct evidence that we can talk about metamorphic magnets and that they behave as predicted by theory,” Krempasky says.

This grouping of electrons appears to originate from the nonmagnetic tellurium atoms in the crystal structure, which separates the magnesium’s magnetic charge into each plane, allowing for its unusual rotational symmetry.

“It’s really amazing to prove that these substances actually exist,” he says. Richard Evans At York University, UK. Not only can electrons in alternating magnets move more freely than electrons in antiferromagnets, but this new type of magnet has no external magnetic fields like ferromagnets, so it could be used to create non-interfering magnetic devices. Evans says. each other.

This characteristic can increase the storage capacity of your computer’s hard drive. This is because commercially available devices are packed with ferromagnetic materials so tightly that external magnetic fields in the material begin to interfere. AC magnets can be packed more densely.

They say this magnet could even lead to spintronic computers that use magnetic spins instead of electrical current to perform measurements and calculations. joseph barker At the University of Leeds in the UK, memory and computer chips have been combined into a single device. “This may give more hope to the idea that spintronic devices can become a reality,” Barker says.

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Source: www.newscientist.com

New technology uses magnetism to control light sources

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Researchers have developed a new method to create transparent magnetic materials using laser heating. This breakthrough is crucial for the integration of magneto-optic materials and optical circuits, a major challenge in this field. This is expected to lead to advances in miniature magneto-optical isolators, miniature lasers, high-resolution displays, and miniature optical devices. Credit: SciTechDaily.com

A new laser heating technique by a Japanese research team enables the integration of transparent magnetic materials into optical circuits, paving the way for advanced optical communication devices.

In a major advance in optical technology, researchers at Tohoku University and Toyohashi University of Technology have developed a new method to create transparent magnetic materials using laser heating. This breakthrough, recently published in the journal Optical Materials, presents a new approach to integrating magneto-optic materials and optical devices, a long-standing challenge in the field.

“The key to this result is that we used a special laser heating technology to create a transparent magnetic material called cerium-substituted yttrium iron garnet (Ce:YIG),” said Taichi Goto, associate professor at Tohoku University’s Institute of Electrical Communication. he points out. (RIEC) and study co-author. “This method addresses the critical challenge of integrating magneto-optic materials into optical circuits without causing damage, an issue that has hindered progress in miniaturizing optical communication devices.”

Laser heating setup for preparing transparent magnetic materials.Credit: Taichi Goto et al.

Magneto-optical isolators in optical communications

Magneto-optical isolators are essential for achieving stable optical communications. These act like traffic lights at traffic lights, allowing movement in one direction but not the other. Integrating these isolators into silicon-based photonic circuits is difficult because they typically require high-temperature processes.

As a result of this challenge, Goto and his colleagues turned to laser annealing, a technique that selectively heats specific areas of a material with a laser. This allows precise control that affects only the target area without affecting the surrounding areas.

Previous work has exploited this to selectively heat bismuth-substituted yttrium iron garnet (Bi:YIG) films deposited on dielectric mirrors. This allows Bi:YIG to be crystallized without affecting the dielectric mirror.

However, problems arise when working with Ce:YIG, whose magnetic and optical properties make it an ideal material for optical devices, as exposure to air causes undesirable chemical reactions.

To get around this, the researchers designed a new device that uses a laser to heat the material in a vacuum, meaning without air. This made it possible to precisely heat small areas (approximately 60 micrometers) without changing the surrounding material.

Impact on optical technology

“Transparent magnetic materials created using this method are expected to greatly facilitate the development of compact magneto-optical isolators that are essential for stable optical communications,” Goto added. “It also opens the door to creating powerful miniature lasers, high-resolution displays, and miniature optical devices.”

Reference: “Vacuum laser annealing of magneto-optical cerium-substituted yttrium-iron-garnet films” Hibiki Miyashita, Yuki Yoshihara, Kanta Mori, Takumi Oguchi, Pan Boy Lim, Mitsuteru Inoue, Kazushi Ishiyama, Taichi Goto, 2023. November 14th, optical materials.
DOI: 10.1016/j.optmat.2023.114530

Source: scitechdaily.com