February 2021

A new theory by Rice University scientists could boost the field of spintronics. Materials theorist Boris Yakobson and graduate student Sunny Gupta at Rice’s Brown School of Engineering describe the mechanism behind Rashba splitting, an effect seen in crystal compounds that can influence their electrons’ “up” or “down” spin states, analogous to “on” or “off” in common transistors.

The left shows the crystal structure of a MoTe2

The Rice model characterizes single layers to predict heteropairs — two-dimensional bilayers — that enable large Rashba splitting. These would make it possible to control the spin of enough electrons to make room-temperature spin transistors, a far more advanced version of common transistors that rely on electric current.

A research team at NTU’s School of Physical and Mathematical Sciences and School of Materials Science and Engineering, led by Associate Professor Gao Weibo, together with colleagues from the Singapore University of Technology and Design, has won substantial funding from Singapore’s National Research Foundation to develop high-performance spintronics devices.

The five-year programme, called “The next generation of spintronics with 2D heterostructures”, aims to develop spintronics devices based on next-generation van der Waals materials, which are strongly bonded two-dimensional (2D) layers of materials that are bound in the third dimension through weaker van der Waals forces.

Yttrium iron garnet is a material which has special magnetic properties. A new process, developed by physicists at Martin Luther University Halle-Wittenberg (MLU), allows for it to be transferred to any material. The new method could advance the production of smaller, faster and more energy-efficient components for data storage and information processing.

Magnetic materials play a major role in the development of new storage and information technologies. Magnonics is an emerging field of research that studies spin waves in crystalline layers. Spin is a type of intrinsic angular momentum of a particle that generates a magnetic moment. The deflection of the spin can propagate waves in a solid body. "In magnonic components, electrons would not have to move to process information, which means they would consume much less energy," explains Professor Georg Schmidt from the Institute of Physics at MLU. This would also make them smaller and faster than previous technologies.

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 multi-institutional team which included researchers from the Department of Energy's Oak Ridge National Laboratory, the University of Tennessee, Purdue University and D-Wave Systems, succeeded in generating accurate results from materials science simulations on a quantum computer that can be verified with neutron scattering experiments and other practical techniques.

The researchers used the power of quantum annealing, a form of quantum computing, by embedding an existing model into a quantum computer. Their unique approach proved that quantum resources are capable of studying the magnetic structure and properties of materials, which could lead to a better understanding of spin liquids, spin ices and other novel phases of matter useful for data storage and spintronics applications.

Antiferromagnetic (AFM) spintronics are devices or components for electronics that couple a flowing current of charge to the ordered spin 'texture' of specific materials. The successful development of AFM spintronics could have important implications, as it could lead to the creation of devices or components that surpass Moore's law. But it seems that finding materials with the exact characteristics necessary to fabricate AFM spintronics is highly challenging.

Researchers at the Lawrence Berkeley National Laboratory, UC Berkeley and the National High Magnetic Field Laboratory in Tallahassee have recently identified a new quantum material (Fe_1/3 + _δNbS₂) that could be used to fabricate AFM spintronic devices. In their most recent papers, they demonstrated the feasibility of using this material for two AFM spintronics applications.