Take an altermagnet, put it under an x-ray machine, change the polarizing filter and watch the material absorb the light. It sounds like an experiment from a physics class, but in fact it is a groundbreaking experiment that lead to a remarkable discovery by physicists from Masaryk University, the Czech Academy of Sciences, Osaka Metropolitan University and the University of Nottingham.
A peculiar manifestation of magnetism of a seemingly non-magnetic material, the so-called altermagnet, was predicted several months ago and recently experimentally confirmed. Altermagnets, a class of materials identified by the scientists from the Institute of Physics of the Czech Academy of Sciences, open new prospects , for example, in the production of chips and electronics.
The magnetic circular dichroism, the phenomenon employed in the experiments, relies on the absorption of light being dependent on its polarisation state. This phenomenon is routinely used to study common magnets (ferromagnets). The discovery consists in the dichroism being observed for the first time in a material that appears non-magnetic from outside, because its magnetic moments are arranged in an anti-parallel fashion. Specifically, a thin layer of manganese telluride (MnTe) has been used. An international team of scientists reported their research and observations in Physical Review Letters.
Altermagnets are materials which, according to the scientists, represent a promising platform for, e.g., a new generation of memory devices and their industrial production. They are not sensitive to perturbing magnetic fields and do not generate any stray fields themselves. "They could have a very practical use, for example, in the production of chips that would be more resistant to magnetic fields and possible deterioration," according to physicist Kuneš from Masaryk University, Faculty of Science.
The so-called spintronic devices based on altermagnets could bring significantly higher processing rates. Spintronics is not just a theory as reflected by its applications, for example, in reading (scanning) heads of some electronic devices or in MRAM type memories. In order to experimentally confirm their calculations and theories, the scientists prepared thin layers of MnTe at the University of Nottingham and transported them under ultra-high vacuum almost 200 kilometers to the British National Laboratory's Diamond Light Source synchrotron X-ray facility near Oxford.
A synchrotron is a large circle with a circumference of hundreds of meters, in which electrons can be accelerated to a velocity close to the speed of light. This is where an intense radiation, such as X-rays, is produced. The physicists exposed a layer of manganese telluride to this radiation and gradually changed its wavelength. Then they measured the differences in the absorption of right-handed and left-handed circularly polarized light. "The experiments carried out in the synchrotron not only confirmed the theoretical prediction, but also represented the first observation of this phenomenon," explains the significance of the discovery, a co-author of the theoretical part, Kuneš.
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