Magnetic monopoles have been found in hematite by Cambridge researchers, opening up new potential for cutting-edge, environmentally friendly computing technology. This observation of emergent monopoles in a natural magnet for the first time may open up new directions for the study of quantum materials.
Magnetic monopoles, or isolated magnetic charges, have been found by researchers in a rust-related material. This finding could lead to the development of quicker and greener computing technology.
Using a method called diamond quantum sensing, scientists from the University of Cambridge were able to see whirling swirls and weak magnetic signals on the surface of hematite, a form of iron oxide.
Swirling Textures and Emerging Monopoles
The researchers noticed that the collective behavior of several spins—a particle’s angular momentum—leads to the formation of magnetic monopoles in hematite. These monopoles move like small magnetic hockey pucks across the hematite’s surface’s whirling swirls. This is the first time that emergent monopoles from nature have been seen in an experiment.
Additionally, as if there were a secret code connecting the two, the research has demonstrated a direct correlation between the magnetic charges of materials such as hematite and the previously unknown whirling swirls. The findings are published today (December 5) in the journal Nature Materials and may help to enable next-generation logic and memory applications.
Perspective on Magnetic Monopoles across History
A fridge magnet or the Earth itself must always exist as a pair of magnetic poles that cannot be isolated, according to the equations of James Clerk Maxwell, the titan of Cambridge physics.
The research’s principal investigator, Professor Mete Atatüre, stated, “The magnets we use on a daily basis have two poles: north and south.” It was theorized in the 19th century that monopolies might exist. However, James Clerk Maxwell disagreed in one of his fundamental equations for the study of electromagnetic.
Head of Cambridge’s Cavendish Laboratory, Atatüre once worked under Maxwell. He said, “It would be like finding a missing puzzle piece that was assumed to be lost if monopoles did exist and we were able to isolate them.”
Emerging Techniques and Joint Research
Scientists proposed a possible mechanism for monopoles to exist in a magnetic substance about fifteen years ago. This potential outcome depended on the north and south poles being extremely apart from one another, making each pole appear isolated locally in an unusual substance known as spin ice.
There is, nevertheless, a different approach to monopole discovery that makes use of the idea of emergence. The concept of emergence states that traits that are either greater than or distinct from the sum of their parts can arise from the combination of numerous physical things.
Collaborating with associates from Oxford University and National University of Singapore, the Cambridge scholars employed emergence techniques to reveal monopoles dispersed throughout two-dimensional space, effortlessly traversing the undulating patterns on a magnetic substance’s surface.
Ferromagnets and antiferromagnets are the two main classes of materials that have whirling topological textures. Antiferromagnets lack a strong magnetic signature, making them harder to investigate even though they are more stable than ferromagnets.
Antiferromagnets and Quantum Magnetometry of Diamonds
Atatüre and colleagues employ diamond quantum magnetometry, an imaging technique, to explore the behavior of antiferromagnets. With no impact on the material’s behavior, this method precisely measures the magnetic field on its surface by using a single spin—the intrinsic angular momentum of an electron—in a diamond needle.
In the present investigation, hematite, an antiferromagnetic iron oxide substance, was examined by means of this methodology. To their amazement, they discovered quadrupoles, dipoles, and monopoles among other hidden patterns of magnetic charges within hematite.
Co-author Professor Paolo Radaelli of the University of Oxford stated, “Monopoles had been predicted theoretically, but this is the first time we’ve actually seen a two-dimensional monopole in a naturally occurring magnet.”
These monopoles arise through many-body interactions because they are a collective state of many spins revolving around a singularity rather than a single fixed particle. The outcome is a small, locally stable particle that emits a diverging magnetic field, according to Dr. Hariom Jani, the University of Oxford’s co-first author.
Co-first author Dr. Anthony Tan of the Cavendish Laboratory stated, “We’ve demonstrated how diamond quantum magnetometry could be used to unravel the mysterious behavior of magnetism in two-dimensional quantum materials, which could open up new fields of study in this area.” Because of their smaller magnetic fields, direct imaging of these textures in antiferromagnets has always proven difficult.
The work emphasizes the promise of diamond quantum magnetometry as well as its ability to reveal and explore obscure magnetic phenomena in quantum materials. These whirling textures covered in magnetic charges have the potential to drive extremely quick and energy-efficient computer memory logic if they are managed.
Reference: Anthony K. C. Tan, Hariom Jani, Michael Högen, Lucio Stefan, Claudio Castelnovo, Daniel Braund, Alexandra Geim, Matthew S. G. Feuer, Helena S. Knowles, Ariando Ariando, Paolo G. Radaelli, and Mete Atatüre, “Revealing emergent magnetic charge in an antiferromagnet with diamond quantum magnetometry,” published in Nature Materials on December 5, 2023.
The European Union, the Royal Society, the Sir Henry Royce Institute, and the Engineering and Physical Sciences Research Council (EPSRC), a division of UK Research and Innovation (UKRI), all provided financial support for the study.