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Researchers at the University of Vienna have designed a new 3D magnetic nanorial, where magnetic monopoles emerge due to increasing magnetic frustration among nanoelements, and are stable at room temperature. Credit: © Sabri Koraltan University of Vienna
Three-dimensional (3D) nano-arrays promise a new era in modern solid-state physics with many applications in photonics, biomedicine and spintronics. The realization of 3D magnetic nano-architectures could enable ultra-fast data storage devices with low power consumption. Due to competing magnetic interactions in these systems, magnetic charges or magnetic monopoles can emerge, which can be used as mobile binary information carriers. Researchers at the University of Vienna have now designed the world’s first 3D artificial spin-ice array to harbor unbound magnetic charges. The results published in the journal Npj calculation materials present a first theoretical demonstration that, in the new network, the magnetic monopoles are stable at room temperature and can be directed on demand by external magnetic fields.
Emerging magnetic monopoles are observed in a class of magnetic materials called spin ice. However, atomic scales and low temperatures required for their stability limit their controllability. This led to the development of 2D artificial spin ice, where single atomic moments are replaced by magnetic nano-islands arranged on different lattices. Scaling has allowed the study of emerging magnetic monopoles on more accessible platforms. Reversing the magnetic orientation of specific nano-islands propagates the monopoles a vertex further, leaving a trail behind them. This trace, the Cordes of Dirac, necessarily stores energy and binds the monopoles, limiting their mobility.
Researchers around Sabri Koraltan and Florian Slanovc, and led by Dieter Suess at the University of Vienna, have now designed a first 3D artificial spin ice array that combines the advantages of atomic and 2D artificial spin ice.
In cooperation with the Nanomagnetism and Magnetism group at the University of Vienna and the theoretical division of the Los Alamos Laboratory, USA, the advantages of the new network are investigated using micromagnetic simulations. Here, 2D flat nano-islands are replaced by magnetic rotating ellipsoids, and a three-dimensional lattice with high symmetry is used. “Due to the degeneration of the ground state, the tension of the Dirac strings vanishes by loosening the magnetic monopoles”, notes Sabri Koraltan, one of the first authors of the study. The researchers took the study to the next stage, where, in their simulations, a magnetic monopoly propagated through the network by applying external magnetic fields, demonstrating its application as carriers of information in a nano -3D magnetic network.
Sabri Koraltan adds: “We are using the third dimension and the high symmetry of the new lattice to untie the magnetic monopoles and move them in the desired directions, almost like real electrons. Other lead author Florian Slanovc concludes: “The thermal stability of monopoles around room temperature and above could lay the groundwork for a revolutionary new generation of 3D storage technologies.
Reference: “Tension-free Dirac strings and directed magnetic charges in 3D artificial spin ice” by Sabri Koraltan, Florian Slanovc, Florian Bruckner, Cristiano Nisoli, Andrii V. Chumak, Oleksandr V. Dobrovolskiy, Claas Abert and Dieter Suess, 5 August 2021, Npj calculation materials.
DOI: 10.1038 / s41524-021-00593-7
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