Future Information Technologies: New combinations of materials for producing magnetic monopoles

X-PEEM images show the orientation of magnetic domains in the permalloy film overlaid on the superconducting dot (dashed square) before (left image) and after the write process (right image). In this sample the domains (arrows, right image) are reorientied in a monopole pattern.

X-PEEM images show the orientation of magnetic domains in the permalloy film overlaid on the superconducting dot (dashed square) before (left image) and after the write process (right image). In this sample the domains (arrows, right image) are reorientied in a monopole pattern. © HZB

An international collaboration at BESSY II has discovered a new method to inscribe exotic magnetic patterns such as magnetic monopoles into thin ferromagnetic films. Such unconventional orientation of magnetic domains might open a new path for the design of energy efficient data storage. The new materials system consists of regular arrays of superconducting YBaCuO-dots covered with an extremely thin permalloy film. A shortly applied external magnetic field leads to the creation of supercurrents within the superconducting dots. These currents produce a complex magnetic field pattern, which is inscribed into the permalloy film above. The results are published in Advanced Science.

Magnetic patterns such as monopoles or skyrmions (stable vortices) are promising options for fast and energy efficient data storage. However obtaining and manipulating such magnetic structures is not easy. Now, Dr. Sergio Valencia and his colleagues at HZB, in collaboration with the materials science institute of Barcelona, have discovered an interesting new materials system which could do the trick. The samples consisted of regular arrays of superconducting YBaCuO-dots, approximately 20 micrometer in diameter and coming in different geometries. Valencia and his team covered these microstructures with an extremely thin film of ferromagnetic iron-nickel-alloy, a so called permalloy.

Complex magnetic patterns

The experiments were done at low temperatures (50 K), allowing the YBaCuO-dots to be superconducting. To change the magnetic domains inside the permalloy, an external magnetic field, perpendicular to the sample plane, was shortly applied. This external field, not enough to reorient the magnetic domains of permalloy, lead to the creation of a so-called supercurrent within the superconducting dots. Such superconducting currents do persist even after the removal of the external magnetic field and produce themselves a complex magnetic field pattern.

Mapping at BESSY II

It is this magnetic pattern, which does rearrange the magnetic domains of the permalloy film on top. It was possible, to reorient all domains pointing toward or away from a common centre, similar to magnetic monopoles. Valencia and his colleagues were able to map the magnetic domains of the permalloy by means of X-ray photoelectron emissions microscopy (X-PEEM and XMCD) at BESSY II.

Monopoles and skyrmions

Computer simulations reaffirm how such magnetic patterns are created in the permalloy film via the interaction with the superconducting dots. Choosing different geometries and arrangements of dots can produce and control a multitude of exotic magnetic patterns similar to monopoles as well as skyrmions, a type of stable vortex. “I am quite optimistic that it is possible to miniaturise such patterns to facilitate their implementation in magnetic memories, for example. What is more, we even have some ideas on how to stabilise such magnetic structures at room temperature”, Valencia says.


The paper on "Encoding Magnetic States in Monopole-Like Configurations Using Superconducting Dots" is published in Advanced Science, Open Access.

DOI: 10.1002/advs.201600207

arö

  • Copy link

You might also be interested in

  • Alternating currents for alternative computing with magnets
    Science Highlight
    26.09.2024
    Alternating currents for alternative computing with magnets
    A new study conducted at the University of Vienna, the Max Planck Institute for Intelligent Systems in Stuttgart, and the Helmholtz Centers in Berlin and Dresden takes an important step in the challenge to miniaturize computing devices and to make them more energy-efficient. The work published in the renowned scientific journal Science Advances opens up new possibilities for creating reprogrammable magnonic circuits by exciting spin waves by alternating currents and redirecting these waves on demand. The experiments were carried out at the Maxymus beamline at BESSY II.
  • BESSY II: Heterostructures for Spintronics
    Science Highlight
    20.09.2024
    BESSY II: Heterostructures for Spintronics
    Spintronic devices work with spin textures caused by quantum-physical interactions. A Spanish-German collaboration has now studied graphene-cobalt-iridium heterostructures at BESSY II. The results show how two desired quantum-physical effects reinforce each other in these heterostructures. This could lead to new spintronic devices based on these materials.
  • Green hydrogen: MXenes shows talent as catalyst for oxygen evolution
    Science Highlight
    09.09.2024
    Green hydrogen: MXenes shows talent as catalyst for oxygen evolution
    The MXene class of materials has many talents. An international team led by HZB chemist Michelle Browne has now demonstrated that MXenes, properly functionalised, are excellent catalysts for the oxygen evolution reaction in electrolytic water splitting. They are more stable and efficient than the best metal oxide catalysts currently available. The team is now extensively characterising these MXene catalysts for water splitting at the Berlin X-ray source BESSY II and Soleil Synchrotron in France.