Antiferromagnetism - Page 2

Researchers have devised a new ultrafast method for controlling magnetic materials, that may enable next-generation information processing technologies.

A possible solution for building faster systems for processing is to use patterns of electron spins, called spin waves, to transfer and process information much more rapidly than in conventional computers. So far, a major challenge has been in manipulating these ultrafast spin waves to do useful work. Announcing a significant step forward, researchers from The University of Texas at Austin and MIT have developed a method to precisely manipulate these ultrafast spin waves using tailored light pulses. Their findings are detailed in two studies in Nature Physics, led by MIT graduate student Zhuquan Zhang, University of Texas at Austin postdoctoral researcher Frank Gao, MIT’s professor of chemistry Keith Nelson and UT Austin assistant professor of physics Edoardo Baldini.

Researchers from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS), led by Associate Prof. Li Xingxing and Prof. Yang Jinlong, recently developed a novel chemical method for two-dimensional metal-organic lattices.

In spintronics, it is paramount to develop an efficient way to reversibly control the spin order of materials. Though various physical methods have been proposed, chemically achieving this has posed significant challenges. The researchers proposed the utilization of the well-recognized lactim−lactam tautomerization process to reversibly modulate the magnetic phase transition in two-dimensional (2D) organometallic lattices. This could offer new pathways for controlling the electrical and magnetic characteristics of materials.

Researchers at China's Hefei University of Technology, University of Science and Technology of China, South China University of Technology, Chinese Academy of Sciences (CAS), Anhui University, Australia's RMIT University, University of New South Wales, Saudi Arabia's Al-Baha University and University of Jeddah have reported magnetism in a quasi-2D magnet Cr_1.2Te₂, observed at room temperature (290 K). 

By intercalating protons into van der Waals ferromagnet Cr_1.2Te₂ nanoflakes, the group of researchers successfully induced a room-temperature magnetic phase transition from ferromagnetism to antiferromagnetism.

Researchers at Johannes Gutenberg University Mainz, the University of Konstanz and Tohoku University in Japan have increased the diffusion of magnetic whirls, so called skyrmions, by a factor of ten.

Science often does not simply consider the spin of an individual electron, but rather magnetic whirls composed of numerous spins. These whirls, called skyrmions, emerge in magnetic metallic thin layers and can be considered as two-dimensional quasi-particles. On the one hand, the whirls can be deliberately moved by applying a small electric current to the thin layers; on the other hand, they move randomly and extremely efficiently due to diffusion. The feasibility of creating a functional computer based on skyrmions was demonstrated by a team of researchers from Johannes Gutenberg University Mainz (JGU), led by Professor Dr. Mathias Kläui, using an initial prototype. This prototype consisted of thin, stacked metallic layers, some only a few atomic layers thick.

Researchers from MIT and Tohoku University have reported a representative effect of the anomalous dynamics at play when an electric current is applied to a class of magnetic materials called non-collinear antiferromagnets. 

Non-collinear antiferromagnets have properties distinct from conventional magnetic materials—in traditional collinear magnets, the magnetic moments align in a collinear fashion. However, in non-collinear ones, the moments form finite angles between one another. Scientists describe these non-collinear arrangements as a single order parameter, the octupole moment, which has been demonstrated to be critical for determining the exotic properties of the materials.

A team of researchers from the DOE/Argonne National Laboratory and U.S. additional laboratories and universities have reported a mechanical response across a layered magnetic material tied to changing its electron spin. This response could have important applications in nanodevices requiring ultra-precise and fast motion control.

A little over a century ago, physicists Albert Einstein and Wander de Haas reported a surprising effect in ferromagnets: if you suspend an iron cylinder from a wire and expose it to a magnetic field, it will start rotating if you simply reverse the direction of the magnetic field. "Einstein and de Haas's experiment is almost like a magic show," said Haidan Wen, a physicist in the Materials Science and X-ray Science divisions of the U.S. Department of Energy's (DOE) Argonne National Laboratory. ​"You can cause a cylinder to rotate without ever touching it."

Researchers from Purdue University, Pennsylvania State University and Japan's National Institute for Materials Science (NIMS) have reported electrically tunable moiré magnetism in twisted double bilayers (a bilayer on top of a bilayer with a twist angle between them) of layered antiferromagnet chromium triiodide. 

Using magneto-optical Kerr effect microscopy, the team observed the coexistence of antiferromagnetic and ferromagnetic order with non-zero net magnetization—a hallmark of moiré magnetism. Such a magnetic state extends over a wide range of twist angles (with transitions at around 0° and above 20°) and exhibits a non-monotonic temperature dependence. The researchers also demonstrated voltage-assisted magnetic switching. The observed non-trivial magnetic states, as well as control via twist angle, temperature and electrical gating, are supported by a simulated phase diagram of moiré magnetism.

A group of physicists, led by Prof. SHAO Dingfu from the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences (CAS), has predicted "parallel circuits" of spin currents in antiferromagnets, which can accelerate spintronics.

Spin-polarized electric currents play a central role in spintronics, due to the capabilities of manipulation and detection of magnetic moment directions for writing and reading 1s and 0s. Currently, most spintronic devices are based on ferromagnets, where the net magnetizations can efficiently spin polarize electric currents. Antiferromagnets, with opposite magnetic moments aligned alternately, are not quite as investigated but may promise even faster and smaller spintronic devices.

Researchers from the University of Nottingham, Diamond Light Source, Czech Academy of Sciences and The University of New South Wales have shown for the first time how electrical creation and control of magnetic vortices in an antiferromagnet can be achieved, a discovery that could increase the data storage capacity and speed of next generation devices.

The team used magnetic imaging techniques to map the structure of newly formed magnetic vortices and demonstrate their back-and-forth movement due to alternating electrical pulses. 

Researchers from Tohoku University in Japan, University of California Riverside and the Massachusetts Institute of Technology detail a decade of research advancements in the emerging field of antiferromagnetic spintronics that holds the promise of moving beyond today’s world of electrons moving through semiconductors.

As computers and other electronic devices become faster and more powerful, they are coming closer to a physical limitation caused by heat generated by the electrons that carry information as they move through semiconductors. “Making heat is a fundamental limit that will prevent the further development of electronic devices. So, we are basically hitting a bottleneck because our computers are way faster than they used to be two decades ago,” said Ran Cheng, an assistant professor of electrical and computer engineering with UCR’s Bourns College of Engineering. Workarounds like cooling systems can go only so far as artificial intelligence, machine learning, video streaming, and other applications demand faster and faster computer processing and memory retrievals.