Recent Spintronic News - Page 2

Unusual magnetoresistance (UMR)—a change in resistivity when magnetization rotates perpendicular to the current—has long puzzled researchers. Traditionally linked to spin Hall magnetoresistance (SMR) and other spin-current-based models, UMR has been widely observed even in systems where these mechanisms should not apply. This inconsistency has fueled a proliferation of alternative explanations, from Rashba-Edelstein MR to orbital Hall MR.

Now, a study led by Prof. Lijun Zhu (Institute of Semiconductors, CAS) and Prof. Xiangrong Wang (CUHK) provides experimental evidence that UMR has a far simpler and universal origin: interfacial electron scattering governed jointly by the magnetization vector and interfacial electric field. Dubbed two-vector magnetoresistance, this model reproduces key features of UMR—including giant signals in single-layer magnetic metals, high-order contributions, and a striking universal sum rule—without invoking spin or orbital currents or crystalline symmetry.

Antiferromagnets are attracting growing attention as promising complements to conventional ferromagnets. While their properties have been extensively studied, clear demonstrations of their technological advantages have remained elusive. Now, researchers from Tohoku University, the National Institute for Materials Science (NIMS), and the Japan Atomic Energy Agency (JAEA) managed to provide compelling evidence of the unique benefits of antiferromagnets. Their recent study shows that antiferromagnets enable high-speed, high-efficiency memory operations in the gigahertz range, outperforming their ferromagnetic counterparts.

The team used the chiral antiferromagnet Mn₃Sn, whose spins form a non-collinear arrangement, as the medium for writing digital information. They fabricated a nanoscale Mn₃Sn dot device and successfully induced coherent rotation of its antiferromagnetic texture using electric currents. This enabled fast, high-fidelity control of spin ordering.

A recent study by teams from the Korea Institute of Science and Technology (KIST), DGIST, Yonsei University, Seoul National University, University of Kashmir, Kunsan National University and Johannes Gutenberg University Mainz presented a device principle that can utilize "spin loss," which was previously thought of as a simple loss, as a new power source for magnetic control. The team's discovery could offer a new approach to significantly improving the efficiency of spintronics devices.

The team identified a new physical phenomenon that allows magnetic materials to spontaneously switch their internal magnetization direction without external stimuli. Magnetic materials are key to the next generation of information processing devices that store information or perform computations by changing the direction of their internal magnetization. For example, if the magnetization direction is upward, it is recognized as '1', and if it is downward, it is recognized as '0', and data can be stored or computed. Traditionally, to reverse the direction of magnetization, a large current is applied to force the spin of electrons into the magnet. However, this process results in spin loss, where some of the spin does not reach the magnet and is dissipated, which has been considered a major source of power waste and poor efficiency.

Rice University researchers have found that creases in 2D materials can control electrons’ spin with record precision, opening the door to compact, energy-efficient electronic devices.

While the field of spintronics faces a challenge in the form of information encoded in spins that tends to quickly decay when electrons scatter and collide with atoms, the Rice team now discovered that bending atomically thin layers of materials like molybdenum ditelluride gives rise to a unique spin texture called persistent spin helix, or PSH, which can preserve spin state even in scattering collisions.

Establishing robust isolated spins on solid surfaces is crucial for fabricating quantum bits or qubits, sensors, and single-atom catalysts. An isolated spin is a single spin that is shielded from external interactions. Since isolated spins can maintain their state for long periods, they are ideal for use as qubits, the basic units of quantum computation, and for ultrafast spintronic memory. Significant research has been dedicated to identifying materials capable of producing a stable isolated quantum spin and candidates include single atoms of transition metals such as copper (Cu) in the Cu-phthalocyanine molecule (CuPc), molecular magnets, nitrogen-vacancy centers in diamonds, and two-dimensional layered materials.

One way to detect an isolated spin is by observing a zero-bias peak (ZBP) in the electrical conductance of, for example, a noble metal substrate containing a CuPc molecule. The ZBP results from the interaction between conduction electrons on the substrate and the isolated spin. So far, the engineering of these ZBPs has been mainly limited to noble metal surfaces, such as gold and silver. These surfaces are rich in conduction electrons, which, while useful for ZBP, can also scatter a spin and flip its state, causing it to disturb the intrinsic spin state. This makes them unsuitable for use as qubits. As a solution, researchers have turned to insulating films, which lack conduction electrons and can host more stable spins. Now, researchers from Chiba University in Japan, led by Associate Professor Toyo Kazu Yamada, demonstrated isolated spins on an insulating solid surface laid over a magnetic substrate.

Scientists at the Ningbo Institute of Materials Technology and Engineering (NIMTE) and additional departments of the Chinese Academy of Sciences, University of Science and Technology of China, ShanghaiTech University and Beihang University have turned a longstanding challenge in electronics - material defects - into a quantum-enhanced solution, paving the way for new-generation ultra-low-power spintronic devices.

Spintronics takes advantage of two additional quantum properties: spin angular momentum, which can be imagined as a built-in "up" or "down" orientation of the electron, and orbital angular momentum, which describes how electrons move around atomic nuclei. By using these extra degrees of freedom, spintronic devices can store more data in smaller spaces, operate faster, consume less energy, and retain information even when the power is switched off. A longstanding challenge in spintronics has been the role of material defects. Introducing imperfections into a material can sometimes make it easier to "write" data into memory bits by reducing the current needed, but this typically comes at a cost: electrical resistance increases, spin Hall conductivity declines, and overall power consumption goes up. This trade-off has been a major obstacle to developing ultra-low-power spintronic devices.

Researchers at Arizona State University show how tiny clusters of copper and oxygen atoms could be tailored for attaining control electron spin properties. The team set out to understand how the magnetic and electronic properties of copper clusters just can be tuned for spintronics applications.

The team used powerful laser pulses to excite neutral copper oxide clusters and watched how they relaxed back to their original state in less than a trillionth of a second. They discovered that by carefully adjusting the balance of copper and oxygen atoms, they could influence how long these excited states last — and crucially, how magnetic the clusters become.

Researchers at the California NanoSystems Institute at UCLA, University of Wisconsin-Madison and the Czech Republic's University of Chemistry and Technology have developed a method for combining magnetic elements with semiconductors. 

The team demonstrated the ability to produce semiconductor materials containing up to 50% magnetic atoms, whereas current methods are often limited to a concentration of magnetic atoms no greater than 5%. Using their process, the scientists created a library of more than 20 new materials that combined magnetic elements such as cobalt, manganese and iron with a variety of semiconductors. 

Researchers at The University of Osaka have developed a new program, “postw90-spin,” that enables high-precision calculations of a novel performance indicator for the spin Hall effect, a phenomenon crucial for developing energy-efficient and high-speed next-generation magnetic memory devices. 

This achievement addresses a long-standing challenge in spintronics research by providing a definitive measure of the spin Hall effect, overcoming ambiguities associated with traditional metrics.

Researchers at Columbia University and the National High Magnetic Field Laboratory recently reported a new mechanism that enables the spin-selective transport of charge carriers in an atomically thin transition metal dichalcogenide, namely tungsten diselenide (WSe₂). Their work could open new possibilities for the development of compact and energy-efficient components for spintronic devices.

"Spin is a fundamental quantum property of electrons, which—in a simplified picture—can be thought of like a tiny internal compass needle pointing either 'up' or 'down,'" said En-Min Shih, first author of the paper. "Spin lies at the heart of magnetism and plays a crucial role in many technologies. For example, in a hard disk drive, information is stored based on whether the magnetization of nanoscale regions points up or down. In this way, you can 'write' information by forcing the spins in a certain region to order along a particular direction, but how do you 'read' the information?". One common approach to "reading" the information stored in spintronic devices entails measuring how easily electrical current passes through magnetized regions in a material. This approach relies on the fact that electrical current is carried by moving electrons, which also have spin.