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


You might also be interested in

  • Small powerhouses for very special light
    Science Highlight
    27.06.2024
    Small powerhouses for very special light
    An international team presents the functional principle of a new source of synchrotron radiation in Nature Communications Physics. Steady-state microbunching (SSMB) allows to build efficient and powerful radiation sources for coherent UV radiation in the future. This is very attractive for applications in basic research as well in the semiconductor industry.
  • New Method for Absorption Correction to Improve Dental Fillings
    Science Highlight
    24.06.2024
    New Method for Absorption Correction to Improve Dental Fillings
    A research team led by Dr. Ioanna Mantouvalou has developed a method to more accurately depict the elemental distributions in dental materials than previously possible. The used confocal micro-X-ray fluorescence (micro-XRF) analysis provides three-dimensional elemental images that contain distortions. These distortions occur when X-rays pass through materials of different densities and compositions. By utilizing micro-CT data, which provides detailed 3D images of the material structure, and chemical information from X-ray absorption spectroscopy (XAS) experiments conducted in the laboratory (BLiX, TU Berlin) and at the synchrotron light source BESSY II, the researchers have improved the method.
  • MXenes for energy storage: Chemical imaging more than just surface deep
    Science Highlight
    17.06.2024
    MXenes for energy storage: Chemical imaging more than just surface deep
    A new method in spectromicroscopy significantly improves the study of chemical reactions at the nanoscale, both on surfaces and inside layered materials. Scanning X-ray microscopy (SXM) at MAXYMUS beamline of BESSY II enables the investigation of chemical species adsorbed on the top layer (surface) or intercalated within the MXene electrode (bulk) with high chemical sensitivity. The method was developed by a HZB team led by Dr. Tristan Petit. The scientists demonstrated among others first SXM on MXene flakes, a material used as electrode in lithium-ion batteries.