Example of Altermagnetism in Chemical Compounds

Alter magnetism works differently from standard magnetism.

Labor Smajkal and Anna Burke Helens

A new type of magnetism has been measured for the first time. Altermagnets, which combine the properties of different classes of existing magnets, can be used to create new types of high-capacity and high-speed memory devices or magnetic computers.

Until the 20th century, only one type was thought of. Permanent magneta ferromagnet, whose effects can be seen in objects with relatively strong external magnetic fields such as fridge magnets or compass needles.

These fields are perpendicular to one direction due to the magnetic spin of the magnet’s electrons.

But, in the 1930s, French physicist Louis Nell discovered another type of magnetism, called antiferromagnetism, where the electron spins are alternately up and down. Although antiferromagnets lack the external fields of ferromagnets, they show interesting internal magnetic properties due to alternating spins.

Then in 2019, The researchers predicted a perturbing electric current in the crystal structure of certain antiferromagnets, known as the anomalous Hall effect., which cannot be explained by the conventional theory of alternating rotation. The current was moving without any external magnetic field.

It seemed, when looking at a crystal in terms of sheets of curvature, that A third type of permanent magnetism may be responsible, called altermagnetism. Altermagnets look like antiferromagnets, but the winding sheets will look the same when rotated through any angle. This would explain 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 type of magnetism.

now, George Krampski At the Paul Scherer Institute in Willingen, Switzerland, and his colleagues have confirmed the existence of an ultramagnet by measuring the electron structure in a single crystal, manganese telluride, which was previously thought to be antiferromagnetic.

To do this, they measured how light bounced off manganese telluride to find the energies and velocities of the electrons inside the crystal. After mapping these electrons, they were found to match almost exactly the predictions given by simulations for electromagnetic 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 electromagnetic properties. “This provided direct evidence that we can talk about altermagnets and they behave exactly as predicted by theory,” says Krempasky.

This electron group appears to come from atoms of tellurium, which is nonmagnetic, in the crystal structure, which separate the magnetic charges of the manganese in their planes and allow unusual rotational symmetry.

“It’s really good confirmation that these materials exist,” he says. Richard Evans With the electrons in electromagnets being more free to move than in antiferromagnets, this new type of magnet also doesn’t have external magnetic fields like ferromagnets, says Evans at the University of York, UK. is that you can use them to make magnetic devices that don’t interfere. with each other.

The property could enhance storage on computer hard drives, as commercial devices contain ferromagnetic material that is packed so tightly that the material’s external magnetic fields begin to show interference – making the ultramagnets more densely packed. can go.

Magnets can also lead to spintronic computers that use magnetic spins instead of currents to make their measurements and calculations. Joseph Barker at the University of Leeds, UK, by combining memory and computer chips into one device. “It probably gives more hope to the idea that we can make spintronic devices a reality,” Barker says.

Article modified on 15 February 2024.

We have corrected when Louis Neill discovered antiferromagnetism and the crystal nomenclature was studied to confirm the existence of ultramagnetism.