Types of magnetism | Ferromagnetism


  • Quantum physicists have finally observed Naraoka ferromagnetism in the lab.
  • Magnetism is essential to the functioning of many electronic devices and machines, and this particular type has implications for quantum computing.
  • An arrangement of electrons behaves like a sliding tile puzzle, while the magnetism remains constant.

    Scientists believe they have made a concrete example of a unusual theoretical form of ferromagnetism first described by a researcher over 50 years ago.

    Nagaoka ferromagnetism, named after the scientist who discovered it, Yosuke Nagaoka, is a special case of the same magnetic forces that make regular fridge-type magnets work.ferro that is, iron, as well as some other metals naturally receptive to magnetism. Identifying it in real life, in this case using a quantum electron system, can help scientists understand how spontaneous ferromagnetism works.

    The analogy for Nagaoka ferromagnetism has been the “15 puzzles», The sliding square puzzle where you have to make a picture or put the numbers in order by sliding one tile at a time. Nagaoka theorized that when all electrons were pointed in the same direction – part of the foundation of quantum mechanics in solid state physics is how electrons are arranged in relation to each other – the whole system would be magnetized.

    In addition, the “perfect case” envisioned by Nagaoka would be impermeable to the layout, hence the angle of the sliding tile. No matter how the electrons mix in the system, they remain magnetized. Their order doesn’t make a difference, so if the electrons were a “set”, say, their arrangements would be like combinations rather than permutations.

    To create a real-life example of the Nagaoka case, quantum physicists at Delft University of Technology created a two-by-two quantum dot array, which are microscopic arrangements of particles that can carry current and light and show patterns. quantum behaviors. They supercooled the lattice and placed electrons on three of the four “squares” of the lattice. (Supercooling in general allows scientists to observe the interaction of subatomic particles because it slows the particles down, relatively speaking.)

    The scientists used a special sensor and electrical system that could measure how the electrons pointed, and indeed, they found that the electrons kept the same homogeneous spin pattern as they moved around the lattice. They say it’s because electrons want to stay in the simplest, lowest energy state, but being the first to observe and document the Nagaoka Effect firsthand is still a big deal.

    The secret of ferromagnetism is one of the greatest mysteries in science. “Roving ferromagnetism is actually one of the most difficult problems in theoretical condensed matter physics,” said a physicist Recount Quanta magazine in 2019. Nagaoka ferromagnetism in particular “has been rigorously studied theoretically but has remained inaccessible in experiments”, the research team explained in his article.

    In this case, traveling ferromagnetism is a specific part of the larger idea of ​​ferromagnetism, “which arises only from long-range interactions of free electrons and whose existence in real systems has been debated for decades”. In other words, distant electrons interact in such a way that they generate a ferromagnetic force, but scientists have not been able to observe this phenomenon. Its existence has therefore remained a controversial hypothesis.

    The researchers suggest that their findings have implications both for the study of ferromagnetism and for the future of quantum computers. If the network can reliably retain its magnetic charge despite all manipulations, this is useful for any system where the manipulation is used to store information or indicate a position. It already seems quite computerized.

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