Memory - Page 4

Researchers from Berkeley Lab, UC Berkeley, UC Riverside, Argonne National Laboratory, Nanjing University and the University of Electronic Science and Technology of China, have developed an ultrathin magnet that operates at room temperature. This development could lead to new applications in computing and electronics - such as high-density, compact spintronic memory devices - and new tools for the study of quantum physics.

"We're the first to make a room-temperature 2D magnet that is chemically stable under ambient conditions," said senior author Jie Yao, a faculty scientist in Berkeley Lab's Materials Sciences Division and associate professor of materials science and engineering at UC Berkeley. "This discovery is exciting because it not only makes 2D magnetism possible at room temperature, but it also uncovers a new mechanism to realize 2D magnetic materials," added Rui Chen, a UC Berkeley graduate student in the Yao Research Group and lead author on the study.

Tohoku University researchers have developed a technology for the nanosecond operation of the spintronics-based probabilistic bit (p-bit) - referred to as the "poor man's quantum bit" (q-bit).

The late physicist R.P. Feynman envisioned a probabilistic computer: a computer that is capable of dealing with probabilities at scale to enable efficient computing. "Using spintronics, our latest technology made the first step in realizing Feynman's vision," said Shun Kanai, professor at the Research Institute of Electrical Communication at Tohoku University and lead author of the study.

Some of the latest advances in spintronics are based on nanometric thin film structures with perpendicular magnetic anisotropy in which the spin currents are used to produce changes in the magnetization of a magnetic layer. This effect is known as spin-orbit torque (SOT) and can be enhanced by suitably engineering multilayer stacks composed by alternated magnetic/non-magnetic metals. The typical structures employed to manipulate the magnetization via SOT are multilayers whose basic constituent is a ferromagnetic layer adjacent to heavy metal(s), which confer large spin-orbit coupling and promote the perpendicular magnetic anisotropy. These systems are the basic elements for spin-orbit torque magnetization switching, used in the next generation of magnetoresistive random access memory (MRAM) devices.

The SpinOrbitronics research team, guided by Dr. Paolo Perna at IMDEA Nanociencia, have observed the emergence of an interfacially enabled increase of the spin-orbit torque when an ultrathin Cu interlayer is inserted between Co and Pt in symmetric Pt/Co/Pt trilayer, in which the effective spin-orbit torque is expected to vanish. The enhancement of SOT is accompanied by a reduction of the spin-Hall magnetoresistance, indicating that the spin memory loss effect in the Co/Cu and Cu/Pt interfaces is responsible of both enhanced SOT and reduction in the spin-Hall magnetoresistance.

A research team, led by Dr. Kim Kyoung-Whan at the Center for Spintronics of the Korea Institute of Science and Technology (KIST), has proposed a new principle which could give a boost to spin memory devices.

Conventional memory devices are classified into volatile memories, such as RAM, that can read and write data quickly, and non-volatile memories, such as hard-disk, on which data are maintained even when the power is off. In recent years, related academic and industrial fields have been working to accelerate the development of next-generation memory that is fast and capable of maintaining data even when the power is off.

Researchers from Seoul National University, Pohang University of Science and Technology, Korea Atomic Energy Research Institute and the Center for Quantum Materials in Korea have designed a prototype of a non-volatile magnetic memory device entirely based on a nanometer-thin layered material, which can be tuned with a tiny current. This finding opens up a new window of opportunities for future energy-efficient magnetic memories based on spintronics.

The choice of magnetic material and device architecture depends on the fact that non-volatile memory technologies have to guarantee safe storage, but also reliable reading and writing access. Hard magnets are perfect for long-term memory storage, because they magnetize very strongly and are difficult to demagnetize. On the contrary, soft magnets are desirable for adding new information to the memory device, because their magnetization can be easily reversed during the writing process. Put simply, ideal magnetic materials can be kept at a hard magnetic state to ensure the stability of the stored information, but be soft on demand.

An international group of researchers, led by the CNRS, developed a new technique that can switch magnetization in only six picoseconds, which is almost 100-times faster than current state-of-the-art spintronics. The new technique is also highly efficient.

The experimental design used to create the ultra-fast magnetization switching included an optical pump directed at the photoconductive switch, which converts the light into 6-picosecond electric pulses. The structure guides these pulses toward the magnet. When the pulses reach the magnet, they trigger the magnetization switching.

Researchers from the University of Arizona discovered that in common Magnetic Tunnel Junctions (MTJ), there's a thin (2D) layer of Iron Oxide. This layer was found to act as a contaminant which lowers the performance achieved by MTJs.

This Iron Oxide layer, however, can also be seen as a blessing - the researchers discovered that the layer behaves as a so-called antiferromagnet at extremely cold temperatures (below -245 degrees Celsius). Antiferromagnets are promising as these can be manipulated at Terahertz frequencies, about 1,000 times faster than existing, silicon-based technology. This is the first research that shows how Antiferromagnets can be controlled as part of MTJs.

Researchers from the National University of Singapore (NUS) have identified a promising spintronics candidate material - few-layer thin semimetal molybdenum ditelluride (MoTe₂).

Semimetals feature material properties that are between metals and semiconductors. The researchers found that an extremely thin (few-layers, almost 2D) MoTe₂ features an intrinsic Spin Hall Effect (SHE).

Researchers from the Tokyo Institute of Technology (Tokyo Tech) developed a new MRAM cell structure that relies on unidirectional spin Hall magnetoresistance (USMR). The new cell structure is reportedly very simple with only two layers which could lead to lower-cost MRAM devices.

The spin Hall effect leads to the accumulation of electrons with a certain spin on the lateral sides of a material. By combining a topological insulator with a ferromagnetic semiconductor, the researchers managed to create a device with giant USMR.

Researchers from Japan's National Institute for Materials Science (NIMS) have managed to introduce a quantum well structure into a conventional magnetic tunnel junction (MTJ). The researchers say that the QW structure can enhance the tunneling magnetoresistance (TMR) ratio by spin-dependent resonant tunnel (SDRT) effect, with a value of 1.5 times comparing with no SDRT case, at room temperature.

The researchers tell us that the key point of the QW formation is the band mismatch between Cr and Fe for majority band, and the mismatch-free Fe/MgAl₂O₄ interface. The finding is not just useful for enhancement of TMR ratio, it also provides a benefit that the TMR ratio could be kept almost constant in a wide bias voltage range of from -1V to 0.5V.