Altermagnetism is effectively a hybrid form of magnetism and ferromagnetism that might become very useful in magnetic storage as well as spintronics in general. In order to practically use it, we first need to be able to control the creation of these altermagnets, which is what researchers have now taken the first steps towards. The research paper by [O. J. Amin] et al. was published earlier this month in Nature. It builds upon the team’s earlier research, including the detection of altermagnetism in manganese telluride (MnTe). This new study uses the same material but uses a photoemission electron microscope (PEEM) with X-rays to image these nanoscale altermagnetic structures.
Visualization of magnetic skyrmions. (Credit: KRISS)
Magnetic skyrmions are stable quasi-particles that can be generated in (some) ferromagnetic materials with conceivable solutions in electronics, assuming they can be created and moved at will. The creation and moving of such skyrmions has now been demonstrated by [Yubin Ji] et al. with a research article in Advanced Materials. This first ever achievement by these researchers of the Korea Research Institute of Standards and Science (KRISS) was more power efficient than previously demonstrated manipulation of magnetic skyrmions in thicker (3D) materials.
Magnetic skyrmions are sometimes described as ‘magnetic vortices’, forming statically stable solitons. For magnetic skyrmions their stability comes from the topological stability, as changing the atomic spin of the atoms inside the skyrmion would require overcoming a significant energy barrier.
In the case of the KRISS researchers, electrical pulses together with a magnetic field were used to create magnetic skyrmions in the ferromagnetic (Fe3GaTe2, or FGaT) film, after which a brief (50 µs) electric current pulse was applied. This demonstrated that the magnetic skyrmions can be moved this way, with the solitons moving parallel to the electron flow injection, making them quite steerable.
While practical applications of magnetic skyrmions are likely to be many years off, it is this kind of fundamental research that will enable future magnetic storage and spintronics-related devices.
Featured image: Direct imaging of the magnetic skyrmions. The scale bars represent 300 nm. (Credit:Yubin Ji et al., Adv. Mat. 2024)
We’ve often said you can make a logic gate out of darn near anything. [The Action Lab] agrees and just released a video showing how he made some logic gates from chains and gears. Along the way, he makes the case that the moving chain is an analog for electric current. The demonstration uses a commercial toy known as Spintronics, but if you are mechanically handy, you could probably devise your own setup using 3D printing or gears.
A spring wound motor is a “battery.” Gears act like resistors and junctions to distribute “current” in multiple directions. Seeing series and parallel resistance as moving chains is pretty entertaining and might help someone new learn those concepts.
Chromium(III) Telluride (Cr2Te3) is an interesting material for (ferro)magnetic applications, with Yao Wen and colleagues reporting in a 2020 Nano Letters paper that they confirmed it to show spontaneous magnetization at a thickness of less than fifty nanometers, at room temperature. Such a 2D ferromagnet could be very useful for spintronics and other applications. The confirmation of magnetization is performed using a variety of methods, including measuring the Hall Effect (HE) and the Anomalous Hall Effect (AHE), the latter of which is directly dependent on the magnetization of the material, rather than an externally applied field.
More recently, in a June 2023 article by Hang Chi and colleagues in Nature Communications, it is described how such epitaxially obtained Cr2Te3 films show a distinct change in the AHE (in the form of sign reversal) depending on the strain induced by the interface with the various types of substrates (Al2O3, SrTiO3) and the temperature, likely owing to the different thermal expansion rates of the film and substrate. Underlying this change in the observed AHE is the Berry phase and the related curvature. This is a phenomenon that was also noted by Quentin Guillet and colleagues in their 2023 article in Physical Review Materials, effectively independently confirming the AHE
Using Cr2Te3 in combination with the appropriate substrate might ultimately lead to spintronics-based memory and other devices, even if such applications will still take considerable R&D.
Top image: Crystal structure of Cr2Te3 thin films. (Credit: Hang Chi et al. 2023)
