A coup in physics? Checks for “irreversible” changes in antiferro magnetism at the atomic level

A coup in physics?  Checks for "irreversible" changes in antiferro magnetism at the atomic level

In the future, storage devices will become more compact and stored data will be better protected from the adverse effects of external magnetic fields.

The device based on magnetic materials has become an important part of our lives, recalls Thomas Jungwirth from the Institute of Physics at ASCR. In power generation and distribution, magnets play an important role in data storage in cloud centers – the advancement of magneto-electronic devices is therefore more important for high-speed memory of computers and smartphones.

Experts at the Academy of Sciences have collaborated with the University of Nottingham in the UK (where Junglewirt lectures) and Uppsala in Sweden to observe the unique magnetic properties of antiferromagnets containing copper, manganese and arsenic (CuMnAs). CEITEC, US Oak Ridge National Laboratory in Brno.

On the left, the crystal structure of the CuMnAs material (copper, manganese, arsenic) and colored arrows show the arrangement of the internal magnetic field. On the right is a diagram of the sharp magnetic domain wall at CuMnAs. Colored arrows show magnetic polarization.

Photo: Institute of Physics AS CR

“We have the opportunity to use the most advanced electron microscopes, which can observe the internal structure of objects at the level of individual atoms with an electron beam. Krisek explained.

Rapid change from atom to atom

During the analysis of the obtained images, the researchers noticed a sharp change in the periodic arrangement of the atomic magnetic fields in the observed antiferro magnet. Assuming that such a change in conventional magnetic material involves gradual and hundreds of thousands of atoms, it is now a rapid transition from atom to neighboring atom – that is, the atomically sharp magnetic domain wall.

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In the opinion of scientists, the so-called walls of the atomic domain are a revolutionary discovery of basic research; Their existence gives a new perspective on understanding the phenomena of magnetic materials. In addition, it sheds light on the problem of microscopic mechanisms behind the operation of ultra fast memory devices made with certain antiferromagnetic materials.

In any case, the antiferromagnets mentioned belong to the “family” of magnetic materials. According to physicist Jangwirth, they are different from ferromagnets because the magnetic fields of their magnetic atoms cancel each other out – they go in opposite directions, for example, they do not stick in the refrigerator or have other interesting macroscopic properties. We usually observe ferromagnets.

In 1970, the French physicist Louis Neil won the Nobel Prize in Physics for his discovery of antiferro magnets. However, he described his findings as interesting but actually useless. Despite the intense research that followed, the practical possibilities were not discovered until experimental antiferromagnetic spintronic devices were first developed.

Although electronic devices, in Jungwirth’s opinion, are based on the manipulation of an electronic charge, spintronic devices are also based on the manipulation of the electron by its other quantum-mechanical properties: the so-called spin. Each crystal of the antiferromagnetic material is bound to a spin state that regulates its internal magnetic structure.

“Special types of spin settings on antiferro magnets later offer unparalleled ideas and functions on ferro magnets,” Jungwirth concluded.

The researchers’ results were published in the journal Science Advances.

Another finding: the magnetic properties of iodide

At some point, the crystals lose their normal structure and turn into a random arrangement called spin glass. Representatives of the J. Herovsky Institute of Physical Chemistry at the Academy of Sciences in the Czech Republic said in a press release in March that the findings could help increase the operating memory of computers in the future.

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