NEW TYPE OF MAGNETISM REPORTED, AND T.T. BROWN WOULD LOVE IT
This important story was spotted and shared by T.M., with our thanks and gratitude, because it is a story that bears watching carefully. A new type of magnetism has been discovered, and it has my mind going in all sorts of directions of high octane speculation. We'll get back to those in a moment, but first the article:
Altermagnetism: A new type of magnetism, with broad implications for technology and research
Note that if this discovery is confirmed, it will be a new addition to "fundamental" physics:
There is now a new addition to the magnetic family: thanks to experiments at the Swiss Light Source SLS, researchers have proved the existence of altermagnetism. The experimental discovery of this new branch of magnetism is reported in Nature and signifies new fundamental physics, with major implications for spintronics.
So what, according to the article, is "altermagnetism." Interestingly enough, the article has to illustrate its operative principles by a comparison to the known types of magnetism:
Magnetism is a lot more than just things that stick to the fridge. This understanding came with the discovery of antiferromagnets nearly a century ago. Since then, the family of magnetic materials has been divided into two fundamental phases: the ferromagnetic branch known for several millennia and the antiferromagnetic branch.
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The fundamental magnetic phases are defined by the specific spontaneous arrangements of magnetic moments—or electron spins—and of atoms that carry the moments in crystals.
Ferromagnets are the type of magnets that stick to the fridge: here spins point in the same direction, giving macroscopic magnetism. In antiferromagnetic materials, spins point in alternating directions, with the result that the materials possess no macroscopic net magnetization—and thus don't stick to the fridge.
Or, if I may put it somewhat differently, in ferromagnetic crystals, the direction of spin - i.e., the axis along which spin occurs - are all cohered, and so to speak, "marching in the same direction at the same tempo", like the photons in a laser beam. Magnetism, as popularly understood, is thus a kind of cohered phenomenon.
And this brings us to the curious phemomenon of altermagnetism:
Altermagnets have a special combination of the arrangement of spins and crystal symmetries. The spins alternate, as in antiferromagnets, resulting in no net magnetization. Yet, rather than simply canceling out, the symmetries give an electronic band structure with strong spin polarization that flips in direction as you pass through the material's energy bands—hence the name altermagnets. This results in highly useful properties more resemblant to ferromagnets, as well as some completely new properties.
The principal implied application of the phenomenon is in information technology and datastorage:
This third magnetic sibling offers distinct advantages for the developing field of next-generation magnetic memory technology, known as spintronics. Whereas electronics makes use only of the charge of the electrons, spintronics also exploits the spin-state of electrons to carry information.
Although spintronics has for some years promised to revolutionize IT, it's still in its infancy. Typically, ferromagnets have been used for such devices, as they offer certain highly desirable strong spin-dependent physical phenomena. Yet the macroscopic net magnetization that is useful in so many other applications poses practical limitations on the scalability of these devices as it causes crosstalk between bits—the information carrying elements in data storage.
More recently, antiferromagnets have been investigated for spintronics, as they benefit from having no net magnetization and thus offer ultra-scalability and energy efficiency. However, the strong spin-dependent effects that are so useful in ferromagnets are lacking, again hindering their practical applicability.
Here enter altermagnets with the best of both: zero net magnetization together with the coveted strong spin-dependent phenomena typically found in ferromagnets—merits that were regarded as principally incompatible.
To put all this somewhat differently and perhaps in an example that will make clearer what is being implied, we all know that in early computer memory hard storage - tapes or floppy disks - that this information could be corrupted or completely erased if those data storage modalities were exposed to strong magnetic fields, and to this day, a computer's hard drive can be wiped by such exposure, due to the strong reliance of memory on ferromagnetic properties. With altermagnetism, however, it might be theoretically feasible to have a magnetic data storage that is more or less impervious to exposure to such strong ferromagnetic fields, since its storage is, in turn, not based on ferromagnetic principles.
So far so good.
It is important to note how the confirmation of altermagnetism was made, i.e., by a variation of common X-ray crystallography and spectroscopy, and how common the phenomenon is:
Obtaining direct experimental proof of altermagnetism's existence required demonstrating the unique spin symmetry characteristics predicted in altermagnets. The proof came using spin- and angle resolved photoemission spectroscopy at the SIS (COPHEE endstation) and ADRESS beamlines of the SLS. This technique enabled the team to visualize a tell-tale feature in the electronic structure of a suspected altermagnet: the splitting of electronic bands corresponding to different spin states, known as the lifting of Kramers spin degeneracy.
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The researchers believe that this new fundamental discovery in magnetism will enrich our understanding of condensed-matter physics, with impact across diverse areas of research and technology. As well as its advantages to the developing field of spintronics, it also offers a promising platform for exploring unconventional superconductivity, through new insights into superconducting states that can arise in different magnetic materials.
"Altermagnetism is actually not something hugely complicated. It is something entirely fundamental that was in front of our eyes for decades without noticing it," says Jungwirth. "And it is not something that exists only in a few obscure materials. It exists in many crystals that people simply had in their drawers. In that sense, now that we have brought it to light, many people around the world will be able to work on it, giving the potential for a broad impact."
With all this in mind, let's take our leap into the canyon of high octane speculation. I suspect that there will be three areas of interest or implications that might develop from this discovery: (1) the coupling of altermagnetism with liquid or "semi-liquid" crystals might produce a kind of magnetism able to alternate between all three states, and thus lose, and then recover, information from collapses from cohered (ferromagnetic) to incoherent (nonferromagnetic) states. It may be possible, with sufficient development of the science, to be able to look at a "disordered" lattice state and reconstruct a higher and more cohered state whence it degraded. If so, then information recovery technologies would take a massive leap forward. Thus (2) a massive leap forward might allow a dramatically new kind of materials science to emerge that would enable one to "dial up" the kind of magnetic state one wanted. We all know of electromagnetics, i.e., that when a strong electrical current is applied, the electromagnet becomes ferromagnatic and picks up materials. Turn the current off, and the materials no longer stick, and fall. But imagine a magnet able to change its state without the current, and one gets the idea. One might be able to have a magnet that would find many or most materials, including antiferromagnetic materials, to be magnetically attracted to it via a kind of "spin coherence resonance". And finally, and probably most fantastically, (3) since altermagnetism involves spin states, and since a relationship to superconductivity has been mentioned in the article itself, might one be able to envision an altermagnetic compound with gravitational and kontrabaric characteristics?
Given what we've heard about T.T. Brown and other investigators of "electro-gravitics," it might just be possible. In this respect, it's important to recall that Brown investigated, for many many years, the properties of non-ferromagnetic rocks, ostensibly with a view to discovering their non-linear properties and "gravitic" characteristics. Perhaps, just perhaps, with altermagnetism, we might have found the phenomenon, or at least, now have a name for and a clearer understanding of it. Time, and investigation, will tell. But I strongly suspect that someone out there will take some known altermagnetic material, and re-perform Brown's experiments with his "gravitators", to see what might happen...
... See you on the flip side...
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