Tag: magnetic sensors

BESSY II: Magnetic ‘microflowers’ enhance local magnetic fields

BESSY II: Magnetic ‘microflowers’ enhance local magnetic fields

A flower-shaped structure only a few micrometres in size made of a nickel-iron alloy can concentrate and locally enhance magnetic fields. The size of the effect can be controlled by varying the geometry and number of ‘petals’. This magnetic metamaterial developed by Dr Anna Palau’s group at the Institut de Ciencia de Materials de Barcelona (ICMAB) in collaboration with her partners of the CHIST-ERA MetaMagIC project, has now been studied at BESSY II in collaboration with Dr Sergio Valencia. Such a device can be used to increase the sensitivity of magnetic sensors, to reduce the energy required for creating local magnetic fields, but also, at the PEEM experimental station, to study samples under much higher magnetic fields than currently possible.

Dr Anna Palau from the Institut de Ciencia de Materials de Barcelona (ICMAB) has developed a special metamaterial that looks like tiny flowers under the scanning electron microscope. The ‘petals’ consist of strips of a ferromagnetic nickel-iron alloy. The microflowers can be produced in various geometries, not only with different inner and outer radii, but also with variable numbers and widths of petals. This flower-shaped geometry causes the field lines of an external magnetic field to concentrate in the centre of the device, resulting on a greatly intensified magnetic field.

Magnetic metamaterials

‘Metamaterials are artificially produced materials with microstructures whose dimensions are smaller than the electromagnetic or thermal waves they are designed to manipulate,’ explains Anna Palau. The physicist is working on magnetic microstructures that can be used in data storage, information processing, biomedicine, catalysis and magnetic sensor technology. By using these metamaterials, the sensitivity of magnetic sensors could be highly increased, as the magnetic field to be detected would be amplified at the center of these systems.

Read more on HZB website

Image: The magnetic microstructure of the nickel-iron alloy leads to a compression of the field lines in the centre.

Credit: A. Palau/ICMAB

A Novel Staircase Pattern in Spin-Stripe Periodicity

A Novel Staircase Pattern in Spin-Stripe Periodicity

SCIENTIFIC ACHIEVEMENT

At the Advanced Light Source (ALS), striped patterns of spins in a magnetic thin film were found to evolve under an applied magnetic field in steps reminiscent of a structure known as the “Devil’s Staircase.”

SIGNIFICANCE AND IMPACT

Such studies are valuable for understanding competing interactions at the atomic level for applications such as magnetic sensors and spintronic devices.

Devilishly complex systems

The “Devil’s Staircase” is a peculiar mathematical function that rises continuously but has no slope (i.e., its derivative is zero almost everywhere). This is because it consists of “runs” (flat sections) connected by “rises” that are fractal: each contains successively smaller copies of the main step, to the infinitesimal limit. Similar structures have emerged in phenomena ranging from earthquakes to charge density waves—systems characterized by competing pressures that result in periods of stability punctuated by short bursts of activity.

Here, researchers report the observation of novel staircase patterns in the evolution of spin-stripe domains in an iron/gadolinium (Fe/Gd) multilayer system. Theoretical modeling that builds on the measurements revealed which of the competing atomic-level interactions in this system is the dominant cause of the staircase structure. The findings help unravel the complex interplay of forces affecting spins in systems relevant to applications in magnetic sensing, information storage, and spintronics.

Read more on the ALS website

Image: A scattering image of one of the sample’s magnetic phases