Tag: magnetic singularities

10 years of research on magnetism at MISTRAL: visualization of hyperbolic Bloch points

10 years of research on magnetism at MISTRAL: visualization of hyperbolic Bloch points

The vector tomography method developed at MISTRAL beamline of the ALBA Synchrotron enables to visualize with nanometric resolution the orientation of the magnetization in magnetic singularities located in magnetic films or multilayers. After 10 years of research, it is reported the first observation of hyperbolic Bloch points, attractive entities for magnetic information transport.

About 70% of all the digitally stored data in the world are located in magnetic bits on disks that have to rotate to reach the location of movable reading sensors. This storage technology, thirty years old, consumes energy and dissipates heat at undesired levels. The search for more efficient methods has been, and still is, an active field of investigation.

Instead of movable parts as disks that require electrical motors, one aims to move the magnetic domains in magnetic ultra-thin films by applying electrical currents or other excitations reducing the operating powers by orders of magnitude. Within this general approach, known as spintronics, the magnetic domains and the walls that separate domains with opposite magnetization are very important actors.

The magnetic structure of the domain walls historically classified in Bloch and Neel types, includes singularities namely skyrmions, merons and Bloch points among others, that have only been observed in recent years. The structure of the magnetization in these singularities may confer them enough energetic stability to be considered as possible dynamic entities for spintronic-based magnetic memories.

As their sizes are nanometric and their magnetic conformation is in general complicated, state of the art microscopy methods are required to visualize them. At the MISTRAL beamline of the ALBA Synchrotron  this topic has been investigated since already ten years and progressively the accuracy of the description of magnetic entities has been improved. The experimental method, known as vector magnetic tomography, allows to visualize with nanometric resolution the orientation of the magnetization in magnetic singularities located in magnetic films or multilayers. It is based on the angular dependence of the dichroic magnetic absorption (different X ray absorption for right and left handed circularly polarized photons).

Read more on ALBA website

Researchers observe topological magnetic monopoles and dipoles in a ferromagnetic material

Researchers observe topological magnetic monopoles and dipoles in a ferromagnetic material

A scientific collaboration between scientists from Universidad de Oviedo and ALBA Synchrotron has achieved a detailed description of magnetic singularities and their interactions from the analysis of data acquired at MISTRAL beamline with the magnetic vector tomography technique. The results of the study, fully experimental not involving simulations and published at Communications Physics, provide a solid ground to understand fundamental knowledge about these singularities, what may have future applications on the design of magnetic devices.

Cerdanyola del Vallès, 31st March 2023 A non-saturated ferromagnetic material exhibits a non-uniform magnetization, forming a mosaic of magnetic domains with different magnetizations. The separation between these domains, domain walls, often intersect which results in exotic magnetization distributions called magnetic singularities. A particular type of magnetic singularities, Bloch points, are the focus of the study performed by researchers from Oviedo University and ALBA Synchrotron, and can be visualized in figure panels b and c.

The work, published at Communications Physics, described how the magnetization behaves around these Bloch points. At their location, the magnetization vectors cancel one another since they point oppositely (-> <- or <- ->), but around them they form complex patterns as the ones shown in figure at panels b and c, with vortex distribution.

A further description of the Bloch singularities is based on analogies with classical electrostatics. The converging and diverging magnetizations remind the electric fields of negative and positive point charges and lead to the concept of emergent magnetic field that, in complete analogy to electric field and electrical charge, allows to define a magnetic charge Q. Within this vision, Bloch points are described as magnetic monopoles of topological magnetic charges Q that create the emergent field Be.

Read more on the ALBA webiste

Image: Scientist at work on the MISTRAL beamline