New fundamental physics was discovered and experiments proved the existence of a new type of magneti

Experiments with the Swiss light source SLS demonstrate the existence of a new type of magnetic force, which has broad implications for technology and research.

Now, a new member has been added to the magnetic family: thanks to experiments with the Swiss light source SLS, researchers have demonstrated the existence of alternating magnetism. The experimental discovery of this new branch of magnetism, published in the journal Nature, marks a new fundamental physics of great significance for spintronics.

Magnetism isn't just something that sticks to the fridge. This understanding arose when antiferromagnets were discovered nearly a century ago. Since then, the family of magnetic materials has been divided into two basic phases: the ferromagnetic branch, known for thousands of years, and the antiferromagnetic branch. The third branch of magnetism, called alternating magnetism, was demonstrated by experiments carried out in the Swiss Light Source (SLS) in an international collaboration led by the Czech Academy of Sciences and the Paul Scherer Institute (PSI).

The fundamental magnetic phase is defined by the magnetic moment (or electron spin) and the specific spontaneous arrangement of the atoms that carry the magnetic moment in the crystal. A ferromagnet is the type of magnet that sticks to the refrigerator: here the spin points in the same direction, creating macroscopic magnetism. In antiferromagnetic materials, the spins point in alternating directions, and the result is that the material has no macroscopic net magnetization and therefore does not stick to the refrigerator. Although other types of magnetism, such as diamagnetism and paramagnetism, have been classified, these magnetisms describe a specific response to an externally applied magnetic field, rather than a spontaneous magnetic sequence in the material.

Alternating magnets have a special combination of spin arrangement and crystal symmetry. The spins alternate, as in antiferromagnets, result in no net magnetization. However, instead of simply canceling out, these symmetries give a structure of electron bands with strong spin polarization, which flips in direction as you pass through the energy bands of the material – hence the name alternating magnet. This results in very useful properties that are more similar to ferromagnets, as well as some completely new ones.

This third magnetic brother offers a clear advantage in the field of development of the next generation of magnetic memory technology, known as spintronics. Electronics only uses the charge of electrons, whereas spintronics also uses the spin state of electrons to carry information.

Although Spintronics has promised to revolutionize IT for years, it is still in its infancy. In general, ferromagnets have been used in such devices because they provide certain highly desirable strong spin-dependent physics. However, the macroscopic net magnetization that is useful in many other applications creates a practical limitation on the scalability of these devices, as it causes crosstalk between bits – the information-carrying element in the data store.

More recently, antiferromagnets have been studied for spintronics because they benefit from the absence of net magnetization and are therefore super scalable and energy efficient. However, the lack of strong spin-dependent effects, which are very useful in ferromagnets, again hinders their practical applicability.

Here we enter alternating magnets that have the advantages of both: zero net magnetization and the coveted strong spin-dependent phenomenon common in ferromagnets—advantages that are considered essentially incompatible.

That's the magic of alternating magnets," said Tomá Jungwirth, the study's principal investigator at the Institute of Physics of the Czech Academy of Sciences. "Before recent theories**, what people thought was impossible actually became possible.

Not so long ago, people began to complain that a new type of magnetism was lurking: in 2019, Jungwirth, together with theoretical colleagues from the Czech Academy of Sciences and the University of Mainz, identified a class of magnetic materials with spin structures that do not conform to the classic description of ferromagnetism or antiferromagnetism.

In 2022, theorists published their ** on the existence of alternating magnetism. They have identified more than 200 alternative magnetic candidates in materials ranging from insulators and semiconductors to metals and superconductors. Many of these materials are well known in the past and have been extensively explored, but their alternating magnetism has not been noted. Due to the tremendous research and application opportunities that alternate magnetism brings, these ** have generated great excitement within the community. The search began.

Obtaining direct experimental proof of the existence of alternating magnets requires the demonstration of the unique spin-symmetry properties in alternating magnets. Evidence comes from spin and angle-resolved optical emission spectra of SIS (Cophee Terminal Station) and ALS's Adress beamlines. This technique allowed the team to visualize a distinct feature in the electronic structure of suspected altermagnets: the ** of electron bands corresponding to different spin states, known as the promotion of Kramers spin degeneracy.

This discovery was made in crystals of manganese telluride, a well-known simple two-element material. Traditionally, this material is considered a classic antiferromagnet because the magnetic moments on adjacent manganese atoms point in opposite directions, producing a net magnetization that disappears.

"Now that we've made it public, many people around the world will be able to do this work. ”

Due to the high precision and sensitivity of our measurements, we can detect characteristic alternations** of energy levels corresponding to opposite spin states, thus proving that manganese telluride is neither a conventional antiferromagnet nor a conventional ferromagnet, but a neo-alternating magnetic branch of magnetic materials," said Juraj Krempasky, a beamline scientist at the PSI Beamline Optics Group, first author of the study.

The Bootstrap Program The beamline that made this discovery has now been disassembled, awaiting SLS 20 upgrades. After two decades of successful scientific research, the Cophee terminal station will be fully integrated into the new "Quest" beamline. "It was in the last photon of the cophee that we carried out these experiments. We are very excited that they have made such an important scientific breakthrough," Krempasky added.

The researchers believe that this new fundamental discovery in magnetism will enrich our understanding of condensed matter physics and have implications for different fields of research and technology. In addition to its strengths in the developing field of spintronics, it provides a promising platform for exploring unconventional superconductivity through new insights into the superconducting states that may occur in different magnetic materials.

Alternating magnetism is actually not a very complex thing. It's something completely basic in front of our eyes for decades without noticing it," Jungwirth said. "And it's not just in a handful of obscure material. It is present in many crystals that people just keep in their drawers. In this sense, now that we have made it public, many people around the world will be able to dedicate themselves to it, with the possibility of having a wide impact.

Reference: "Altermagnetic lifting of kramers spin degeneracy" by J krempaský， l. šmejkal， s. w. d'souza， m. hajlaoui， g. springholz， k. uhlířová， f. alarab， p. c. constantinou， v. strocov， d. usanov， w. r. pudelko， r. gonzález-hernández， a. birk hellenes， z. jansa， h. reichlová， z. šobáň，r. d. gonzalez betancourt， p. wadley， j. sinova， d. kriegner， j. minár， j. h.dil and tJungwirth, February 14, 2024, Nature.

doi： 10.1038/s41586-023-06907-7

Compiled from: scitechdaily