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Scientists manage magnetism at the microscopic level

Scientists take control of magnetism at the microscopic level
The sample (gray) does not have any applied magnetic field and contains left-handed (left inset) and right-handed (right inset) magnetic domain walls. When magnetized (red), the sample’s domain walls move closer together and either annihilate or combine (bottom inset). Credit: Oak Ridge National Laboratory.

Atoms in magnetic materials are organized into regions called magnetic domains. Within each domain, the electrons have exactly the same magnetic orientation. This implies their spins point in exactly the same direction. “Walls” separate the magnetic domains. One kind of wall has spin rotations which are left- or right-handed, referred to as having chirality. When put through a magnetic field, chiral domain walls approach each other, shrinking the magnetic domains.

Researchers are suffering from a magnetic material whose thickness determines whether chiral domain walls have exactly the same or alternating handedness. In the latter case, applying a results in annihilation of colliding domain walls. The researchers combined and electron microscopy to characterize these internal, microscopic features, resulting in better knowledge of the magnetic behavior.

An emerging field of technology called spintronics involves processing and storing information by harnessing an electron’s spin rather than its charge. The opportunity to control this fundamental property could unlock new possibilities for developing gadgets. In comparison to current technology, the unit could store more info in less space and operate at higher speeds with less energy consumption.

Published in Nano Letters, this study demonstrates a method to change the rotational direction and occurrence of domain wall pairs. This suggests a potential route for controlling domain walls’ properties and movement. The outcomes may have implications for technologies predicated on spintronics.

The opportunity to manipulate domain wall movement has remained challenging because typically can randomly switch orientations. Furthermore, domain boundaries move unpredictably when domain sizes are reduced to support higher information storage density. However, a class of materials called chiral magnets shows prospect of mitigating random domain wall behavior. It is because chiral magnets exhibit intricate spin structures, that assist decrease the random reversal of domains.

Researchers from Indiana UniversityPurdue University Indianapolis, Oak Ridge National Laboratory, Louisiana State University, Norfolk State University, the Peter Grnberg Institute, and the University of Louisiana at Lafayette developed a chiral magnetic material by inserting manganese atoms between hexagonal layers of niobium disulfide compounds. By performing neutron experiments at the High Flux Isotope Reactor (HFIR), the team could analyze the magnetic nanostructure of the material when put through different temperatures and magnetic fields.

These measurements were coupled with characterization via Lorentz transmission , allowing a far more complete knowledge of the magnetic behavior. The team’s data claim that changing the thickness of the chiral magnet could cause some domain wall pairs to rotate in opposite directions, referred to as having opposite chirality. Furthermore, the researchers discovered that domain walls with opposite chirality will move toward one another and annihilate when subjected to an external magnetic field. The findings could inform future research on controlling magnetic properties for technological applications.

More info: Sunil K. Karna et al, Annihilation and Control of Chiral Domain Walls with Magnetic Fields, Nano Letters (2021). DOI: 10.1021/acs.nanolett.0c03199

Citation: Scientists manage magnetism at the microscopic level (2022, August 25) retrieved 26 August 2022 from

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