Research / Technical - Page 4

Researchers at Newcastle University, National University of Singapore (NUS) and Japan's National Institute for Materials Science have reported a significant discovery in the field of spintronics based on the unique properties of an ultrathin, two-dimensional material called black phosphorus and how it transports spinning electrons.

Spintronics utilizes the intrinsic spin of electrons to create more energy-efficient devices. Electrons have a spin state of “up” or “down” causing the electrons to act like tiny magnets and manipulating this state has been seen by researchers as crucial for achieving lower power operation in electronic devices. This is because the spin motion of electrons inherently dissipates far less heat than the movement of electrical charge used in traditional electronics. Whilst the phenomenon of spin itself has been widely studied, the challenge has been finding a material with the optimal properties for creating the channels that transport spins.

Researchers have conducted experiments at the Swiss Light Source SLS that resulted in proof of the existence of a new type of magnetism: altermagnetism. The experimental discovery of this new branch of magnetism could signify new fundamental physics, with major implications for spintronics.

Since the discovery of antiferromagnets nearly a century ago, the family of magnetic materials has been divided into two fundamental phases: the ferromagnetic branch known for several millennia and the antiferromagnetic branch. The experimental proof of a third branch of magnetism, termed altermagnetism, was made by an international collaboration led by the Czech Academy of Sciences together with Paul Scherrer Institute PSI. The fundamental magnetic phases are defined by the specific spontaneous arrangements of magnetic moments—or electron spins—and of atoms that carry the moments in crystals.

An international team of researchers has identified a novel state of matter, distinguished by chiral currents at the atomic level. This discovery challenges traditional understandings of magnetic materials and opens up new doors for quantum material applications.

Chirality, a property indicating that a structure cannot be superimposed onto its mirror image, is crucial across various scientific fields, notably in understanding DNA's structure. The research group, led by Federico Mazzola from Ca' Foscari University of Venice, observed these chiral currents through interactions between light and matter. Specifically, they demonstrated that electrons could be ejected from a material's surface with a distinct spin state by employing suitably polarized photons.

Researchers at Newcastle University, National University of Singapore (NUS) and Japan's National Institute for Materials Science have reported on the highly anisotropic spin transport nature of two-dimensional black phosphorus.

In contrast to the conventional movement of charge in electronic devices, spintronics focuses on pioneering devices that manipulate the intrinsic property of electrons known as "spin." Similar to charges in electrons, spin gives electrons a rotational quality like they are rotating around an axis, making them behave like tiny magnets, which have both a magnitude and a direction. The electron spin can exist in one of two states, referred to as spin "up" or spin "down." This is analogous to clockwise or anticlockwise rotation. While traditional electronic devices work by moving charges around the circuit, spintronics operates by manipulating the electron spin. This is important because moving electrical charges around traditional electric circuits necessarily causes some power to be lost as heat, whereas the motion of spin does not intrinsically dissipate as much heat. This characteristic could potentially allow for lower-power device operation.

Higher-order topological insulators, or HOTIs, have attracted attention for their ability to conduct electricity along one-dimensional lines on their surfaces, but this property is quite difficult to experimentally distinguish from other effects. 

By instead studying the interiors of these materials from a different perspective, a team of researchers at the University of Illinois at Urbana-Champaign, Dublin Institute for Advanced Studies, Chinese Academy of Sciences and additional collaborators has identified a surface signature that is unique to HOTIs that can determine how light reflects from their surfaces. 

Researchers at the National Synchrotron Light Source II at Brookhaven National Laboratory, University of California Davis, University of Colorado Springs, Stockholm University, National Institute of Standards and Technology, University of California San Diego, Ca’ Foscari University of Venice, and Elettra Sincrotrone Trieste have conducted an experiment with magnetic materials and ultrafast lasers that could advance energy-efficient data storage.

"We wanted to study the physics of light-magnet interaction," said Rahul Jangid, who led the data analysis for the project while earning his Ph.D. in materials science and engineering at UC Davis under associate professor Roopali Kukreja. "What happens when you hit a magnetic domain with very short pulses of laser light?"

Researchers at Japan's Tokyo Institute of Technology (Tokyo Tech) have demonstrate the concept of Berry phase monopole engineering of the spin Hall effect in non-centrosymmetric silicide TaSi₂.

Image credit: Tokyo Tech

Spin-transfer torque is an important phenomenon that enables ultrafast and low-power spintronic devices. Recently, however, spin-orbit torque (SOT) has emerged as a promising alternative to spin-transfer torque. Many studies have investigated the origin of SOT, showing that in non-magnetic materials, a phenomenon called the spin Hall effect (SHE) is key to achieving SOT. In these materials, the existence of a “Dirac band” structure, a specific arrangement of electrons in terms of their energy, is important to achieving large SHE. This is because the Dirac band structure contains “hot spots” for the Berry phase, a quantum phase factor responsible for the intrinsic SHE. Thus, materials with suitable Berry phase hot spots are key to engineering the SHE.

Scientists at the University of Wisconsin–Madison, University of California, Cornell University, University of Nebraska, Arizona State University and Tsinghua University have found a unique property of the material Ba(Pb,Bi)O₃: it exhibits extremely high spin orbit torque, a property useful in the field of spintronics. The materials was previously found to act as a rare type of superconductor that could operate at higher temperatures. 

The combination of these two properties makes this and similar materials potentially important in developing the next generation of fast, efficient memory and computing devices.

Researchers from Beijing University of Technology, South China University of Technology, Forschungszentrum Jülich and Uppsala University have reported the first experimental evidence of hopfions, which are magnetic spin structures predicted decades ago that have become a fascinating research topic in recent years.

The team used transmission electron microscopy to observe hopfions forming coupled states with skyrmion strings in B20-type FeGe plates. They provided a protocol for nucleating such hopfion rings, which they verified using Lorentz imaging and electron holography. The scientists' results are said to be highly reproducible and in full agreement with micromagnetic simulations. 

Researchers from Japan's RIKEN Center for Emergent Matter Science (CEMS) and Ochanomizu University, UK's  University of Birmingham, Sweden's Lund University, Canada's Université de Sherbrooke, Czech Republic's Nuclear Physics Institute, France's Institut Max von Laue-Paul Langevin (ILL) have advanced low-energy devices based on spintronics, by measuring the dynamics of tiny magnetic vortices.

The team examined the low-energy excitations of the skyrmion state in MnSi by using the neutron spin-echo technique under small-angle neutron scattering conditions. The scientists observed an asymmetric dispersion of the phason excitations of the lattice because of the string-like structure of the skyrmion cores.