Research / Technical

In a recent study, researchers have discovered antiferromagnetism in a real Quasicrystal (QC). The team was led by Ryuji Tamura from the Department of Materials Science and Technology at Tokyo University of Science (TUS), along with Takaki Abe, also from TUS, Taku J. Sato from Tohoku University, and Max Avdeev from the Australian Nuclear Science and Technology Organization and The University of Sydney.

Quasicrystals are solid materials that exhibit an intriguing atomic arrangement. Unlike regular crystals, in which atomic arrangements have an ordered repeating pattern, QCs display long-range atomic order that is not periodic. Due to this 'quasiperiodic' nature, QCs have unconventional symmetries that are absent in conventional crystals. Since their Nobel Prize-winning discovery, condensed matter physics researchers have dedicated immense attention toward QCs, attempting to both realize their unique quasiperiodic magnetic order and their possible applications in spintronics and magnetic refrigeration.

Researchers at the University of California San Diego have developed a new computational approach to accurately model and predict complex spin structures called helimagnetic spin structures, using quantum mechanics calculations. 

“The helical spin structures in two-dimensional layered materials have been experimentally observed for over 40 years. It has been a longstanding challenge to predict them with precision,” said Kesong Yang, professor in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at the UC San Diego Jacobs School of Engineering and senior author of the study. “The helical period in the layered compound extends up to 48 nanometers, making it extremely difficult to accurately calculate all the electron and spin interactions at this scale.”

Researchers from Eindhoven University of Technology, University of Cambridge, Huazhong University of Science and Technology, AMOLF and Diamond Light Source Ltd have created an organic semiconductor that forces electrons to move in a spiral pattern, which could improve the efficiency of OLED displays or power next-generation computing technologies such as spintronics and quantum computing.

The semiconductor they developed emits circularly polarized light—meaning the light carries information about the ‘left or right-handedness’ of electrons. The internal structure of most inorganic semiconductors, like silicon, is symmetrical, meaning electrons move through them without any preferred direction. But in nature, molecules often have a chiral (left- or right-handed) structure. Chirality plays an important role in biological processes like DNA formation, but it is a difficult phenomenon to harness and control in electronics.

Scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory and the University of Washington have reported a new technique that could help advance the development of quantum technology. Their innovation, surface-sensitive spintronic terahertz spectroscopy (SSTS), provides an unprecedented look at how quantum materials behave at interfaces.

With the SSTS technique, a laser pulse is applied to one side of an oxide/metal sample and terahertz radiation is emitted. From the signal, the dynamics of the TO1 surface phonon is detected in the oxide at its interface with the metal. (Image by Argonne National Laboratory.)
 

“This technique allows us to study surface phonons — the collective vibrations of atoms at a material’s surface or interface between materials,” said Zhaodong Chu, a postdoctoral researcher at Argonne and first author of the study. ​“Our findings reveal striking differences between surface phonons and those in the bulk material, opening new avenues for research and applications.”

Researchers at the University of Utah and the University of California, Irvine (UCI), have set out to better understand a property known as spin-torque, that is crucial for the electrical manipulation of magnetization that’s required for the next generations of storage and processing technologies. 

The spintronic prototype device that exploits the anomalous Hall torque effect. Image from: University of Utah

The scientists have discovered a new type of spin–orbit torque, in a recent study that demonstrated a new way to manipulate spin and magnetization through electrical currents, a phenomenon that they’ve dubbed the anomalous Hall torque.

A University of Tokyo research team has shown that the direction of a spin-polarized current can be restricted to only one direction in a single-atom layer of a thallium-lead alloys when irradiated at room temperature. 

This discovery defies conventions as single-atom layers have been thought to be almost completely transparent, in other words, negligibly absorbing or interacting with light. The one-directional flow of the current observed in this study could enable functionality beyond ordinary diodes, paving the way for more environmentally friendly data storage and ultra-fine two-dimensional spintronic devices. 

Researchers at Tohoku University and the University of California, Santa Barbara, have developed new computing hardware that utilizes a Gaussian probabilistic bit made from a stochastic spintronics device. This innovation is expected to provide an energy-efficient platform for generative AI.

As Moore's Law slows down, domain-specific hardware architectures - such as probabilistic computing with naturally stochastic building blocks - are gaining prominence for addressing computationally hard problems. Similar to how quantum computers are suited for problems rooted in quantum mechanics, probabilistic computers are designed to handle inherently probabilistic algorithms. These algorithms have applications in areas like combinatorial optimization and statistical machine learning. 

A team of researchers from CIC nanoGUNE, IKERBASQUE, IMEC and CNRS have reported a spintronic device that leverages proximity effects alone, specifically a 2D graphene-based spin valve. The functioning of this valve relies only on the proximity to the van der Waals magnet Cr₂Ge₂Te₆. Spin precession measurements showed that the graphene acquires both spin–orbit coupling and magnetic exchange coupling when interfaced with the Cr₂Ge₂Te₆. This leads to spin generation by both electrical spin injection and the spin Hall effect, while retaining spin transport. The simultaneous presence of spin–orbit coupling and magnetic exchange coupling also leads to a sizeable anomalous Hall effect.

The primary objective of this recent study was to tackle a long-standing research challenge, namely that of realizing the first-ever seamless 2D spintronic device. The spin valve they developed could enable the manipulation and transport of spin entirely in the 2D plane.

Magnetic skyrmions have so far been treated as two-dimensional spin structures characterized by a topological winding number. However, in real systems with the finite thickness of the device material being larger than the magnetic exchange length, the skyrmion spin texture extends into the third dimension and cannot be assumed as homogeneous.

A 3D reconstruction of a skyrmion derived from X-ray images. Credit: Berkeley Lab

Researchers at Lawrence Berkeley National Laboratory, Swiss Light Source (Paul Scherrer Institute) and Western Digital Research Center have used soft x-ray laminography to reconstruct, with about 20-nanometer spatial (voxel) size, the full three-dimensional spin texture of a skyrmion in an 800-nanometer-diameter and 95-nanometer-thin disk patterned into a 30× [iridium/cobalt/platinum] multilayered film.

In a recent sturdy, researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory and Northern Illinois University discovered that they could use light to detect the spin state in a class of materials called perovskites (specifically in this research methylammonium lead iodide, or MAPbI₃). 

To understand spin, consider electrons orbiting the atomic nucleus. When atoms are close together, they can share some of their outer electrons, which creates a bond between them. Each bond contains two electrons that are ​“paired,” meaning they share an orbital — the region where they move. Now, each of these paired electrons has one of two possible spin states: spin up or spin down. If one electron is spin up, the other is spin down. Since we can’t know exactly which electron has which spin without looking at them, we say they exist in a quantum superposition — a state where they are both spin up and spin down until observed.