Physicists from the University of Augsburg have been able to distinguish chiral systems with similar magnetization but opposite rotation directions using electrical measurements at low temperatures. This is significant for fundamental research on complex magnets and potential applications in magnetic data storage. The results have been published in the journal Nature Physics.
Electric current and magnetic forces are directly related: current-carrying conductors generate a magnetic field, and the magnetic field deflects charged particles perpendicularly to the current and field direction. This phenomenon is called the “Hall effect,” named after its discoverer, Edwin Hall.
The Hall effect is used to study the electrical and magnetic properties of metals. The “ordinary Hall effect” allows us to determine the concentration of charge carriers and their mobility, while an additional contribution called the “anomalous Hall effect” appears in magnets.
At the Institute of Physics at the University of Augsburg, it has now been discovered that the anomalous Hall effect can reveal hidden symmetry. “Despite the same magnetization, two states exhibit distinctly different signals of the anomalous Hall effect, which is a surprising and remarkable discovery,” explains Philipp Gegenwart, professor of Experimental Physics.
The research was conducted on the metallic magnet HoAgGe, which possesses special magnetic properties discovered four years ago by Professor Gegenwart’s team. This material is characterized by a triangular spin configuration of holmium atom’s electron spins.
Due to the simultaneous appeasement of all interaction pairs on each triangle being impossible, a magnetically frustrated state arises. There are energetically degenerate configurations on each triangle, forming what is called spin ice. The spins reside on the edges of the triangles, which resemble entangled Japanese baskets called “Kagome.” Similar principles governing water ice determine the possible configurations of magnetic moments.
In contrast to ordinary magnets, the magnetic moments in spin ice are not aligned in a single direction but possess a complex chiral structure, meaning different rotation directions. They form in an external magnetic field at low temperatures and are characterized by flat planes of magnetization with values of 1/3 and 2/3. The above image depicts two of these structures with similar energy and 1/3 maximum magnetization each.
The research group at the University of Augsburg systematically studied and analyzed the anomalous Hall effect at low temperatures. Surprisingly, different values of the anomalous Hall effect were found for the two 1/3 magnetization structures, visible as red and black curves in the above graph.
Data modeling revealed hidden symmetry: a combination of a 180-degree rotation and inversion of distortion is necessary to transform one structure into another. Conduction electrons scattering on the two different structures have different phase curvatures of their wave functions, leading to a difference in the anomalous Hall effect despite the similar energy and magnetization of the two distinct structures.
More generally, this observation indicates a new potential for measuring the anomalous Hall effect in metals with magnetic frustration and uncovering hidden symmetries and states using electrical measurements. “This could also be interesting in the context of persistent magnetic data storage on the atomic scale,” adds Gegenwart. However, this requires local addressing and selective change of the rotation direction of these structures.
FAQ Section based on the main topics and information presented in the article:
1. How do physicists from the University of Augsburg distinguish chiral magnetic systems?
Physicists from the University of Augsburg use electrical measurements at low temperatures to distinguish chiral systems with similar magnetization but opposite rotation directions.
2. What is the Hall effect?
The Hall effect is a physical phenomenon in which a magnetic field deflects charged particles perpendicularly to the current and field direction. It is used to study the electrical and magnetic properties of metals.
3. How does the anomalous Hall effect appear in magnets?
The anomalous Hall effect is an additional contribution that appears in magnets. It is used to study the magnetic properties of these materials.
4. What was discovered at the University of Augsburg?
At the University of Augsburg, it was discovered that the anomalous Hall effect can reveal hidden symmetry in magnetic structures with similar magnetization but different rotation directions.
5. What are the applications of these discoveries?
Research on the anomalous Hall effect has the potential for application in magnetic data storage on the atomic scale.
6. What are the properties of the HoAgGe magnet?
The HoAgGe magnet has special magnetic properties and is characterized by a triangular spin configuration of holmium atom’s electron spins. It is a magnetically frustrated material.
7. What are the configurations of magnetic moments in spin ice?
In spin ice, the magnetic moments have a complex chiral structure, meaning different rotation directions. Flat planes of magnetization with values of 1/3 and 2/3 are present.
8. How does the anomalous Hall effect differ for different magnetization structures?
The anomalous Hall effect differs for different magnetization structures, even if they have similar energies and magnetizations. This is due to differences in the phase curvatures of conduction electrons.
9. What are the potential applications of measuring the anomalous Hall effect?
Potential applications of measuring the anomalous Hall effect include uncovering hidden symmetries and states in metals with magnetic frustration and achieving persistent magnetic data storage on the atomic scale.
10. What changes are required for the implementation of these discoveries?
The implementation of these discoveries requires local addressing and selective change of the rotation direction of magnetic structures.
Suggested Related Links:
– phys.org – A website featuring news and information on physics and science.
– nature.com – Website of the journal Nature Physics, where the research results were published.
The source of the article is from the blog be3.sk