Room Temperature

Researchers from Kyoto University, Chiba University, The University of Tokyo, Osaka University and Tokai University have found that the direction of spins inside a special type of magnet can be changed rapidly - flipping about every trillionth of a second - without increasing the temperature. They achieved this by applying a strong magnetic field with an oscillation frequency in the terahertz range.

The background for this work, according to the scientists, is the ever-increasing amount of information handled by computers and communication devices, that is driving development of technologies using the terahertz band - around 1012 Hz, a frequency range beyond the conventional gigahertz range of 109 Hz - considered important for the post-5G era. Additionally, memory technologies based on spintronics are expected to use less power to store more information, with antiferromagnets attracting attention because their collective spin-motion mode frequency reaches the terahertz range, making it possible to control spins using terahertz waves. However, conventional spin excitation using electric-field pulses is accompanied by heating or carrier excitation effects that subside relatively slowly, making it difficult to achieve fast spin control. The team has now demonstrated non-thermal spin switching in a canted antiferromagnet by dynamically modifying the magnetic energy landscape using a strong multicycle terahertz magnetic near-field.

Researchers at India's Institute of Nano Science and Technology (INST), an autonomous research institution of Department of Science and Technology (DST), recently produced a transparent conducting interface between two insulating materials with room temperature spin polarized electron gas, which allows for see-through devices with efficient spin currents. 

Prof. Suvankar Chakraverty and his group at INST have produced a 2D Electron Gas (2DEG) with room temperature spin polarization at the interface composed of chemicals LaFeO₃ and SrTiO₃. They grew super lattices and hetero structures of oxide materials to realize new and exotic two-dimensional electron gas at the interface of two insulating oxides that could be useful for next generation quantum devices.

Scientists have long since been trying to use electric fields to control spin at room temperature but achieving effective control has thus far been elusive. In a recent research work, a team from Rensselaer Polytechnic Institute and the University of California at Santa Cruz took a step forward in addressing the issue.

An electron has a spin degree of freedom, meaning that it not only holds a charge but also acts like a little magnet. In spintronics, a key task is to use an electric field to control electron spin and rotate the north pole of the magnet in any given direction. The spintronic field effect transistor harnesses the so-called Rashba or Dresselhaus spin-orbit coupling effect, which suggests that one can control electron spin by electric field. Although the method holds promise for efficient and high-speed computing, certain challenges must be overcome before the technology reaches its true, miniature but powerful, and eco-friendly, potential.

A team of researchers at Politecnico di Milano, University Grenoble Alpes and other institutes worldwide have recently demonstrated the non-volatile control of the spin-to-charge conversion in germanium telluride, a known Rashba semiconductor, at room temperature. Their work could have important implications for the future development of spintronic devices.

The Rashba effect, discovered in 1959, entails a momentum-independent splitting of spin bands in two-dimensional condensed matter systems. In ferroelectric Rashba semiconductors, this effect can be reversed by switching the direction of the ferroelectric polarization. The idea that Rashba spin-splitting in these materials can be controlled was confirmed by a series of first-principle calculations by S. Picozzi and later validated in spectroscopic experiments using germanium telluride, which is thus often considered the 'prototype' of the ferroelectric Rashba class of semiconductors.

Researchers at CIC nanoGUNE BRTA in Spain and University of Regensburg in Germany have recently demonstrated spin precession at room temperature in the absence of a magnetic field in bilayer graphene. In their paper, the team used 2D materials to realize a spin field-effect transistor.

Sketch of the spin field-effect transistor. Image from article

Coherently manipulating electron spins at room temperature using electrical current is a major goal in spintronics research. This is particularly valuable as it would enable the development of numerous devices, including spin field-effect transistors. In experiments using conventional materials, engineers and physicists have so far only observed coherent spin precession in the ballistic regime and at very low temperatures. Two-dimensional (2D materials), however, have unique characteristics that could provide new control knobs to manipulate spin procession.

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.

A team of researchers from Sweden, Finland and Japan have designed a semiconductor component in which information can be efficiently exchanged between electron spin and light at room temperature and above.

Developments in spintronics in recent decades have been based on the use of metals, and these have been highly significant for the possibility of storing large amounts of data. There would, however, be several advantages in using spintronics based on semiconductors, in the same way that semiconductors form the backbone of today's electronics and photonics.

Researchers from Oak Ridge National Laboratory (ORNL), University of California and Lawrence Berkeley National Laboratory have discovered the existence of elusive spin dynamics in quantum mechanical systems.

The team successfully simulated and measured spins - magnetic particles, which can exhibit a motion known as Kardar-Parisi-Zhang in solid materials at varying temperatures. Up until now, scientists have only found evidence of the spin dynamics in soft matter and other classical materials.

Researchers used the Advanced Photon Source (APS), a U.S. Department of Energy Office of Science User Facility at DOE’s Argonne National Laboratory, to study ways to manipulate electron spins and develop new materials for spintronics. The research team, led by Chang-Beom Eom at the University of Wisconsin-Madison, designed a new material that has three times the storage density and uses much less power than other spintronics devices.

Not many of these types of materials exist, especially ones that work at room temperature like this one. If the new material can be perfected, it could aid in the creation of more efficient electronic devices with less tendency to overheat. This is particularly important for advancing the development of low-power computing and fast magnetic memory.

University of Groningen researchers have measured the presence of electron-spin-dependent nonlinearity in a van der Waals heterostructure spintronic device. The team went on to demonstrate its application for basic analog operations such as essential elements of amplitude modulation and frequency sum (heterodyne detection) on pure spin signals, by exploiting the second-harmonic generation of the spin signal due to nonlinear spin injection.

Graphene (light green) with boron nitride (blue) on top. Measuring points indicated in orange.

The researchers also showed that the presence of nonlinearity in the spin signal has an amplifying effect on the energy-dependent conductivity-induced nonlinear spin-to-charge conversion effect. The interaction of the two spin-dependent nonlinear effects in the spin-transport channel leads to a highly efficient modulation of the spin-to-charge conversion effect, which in principle can also be measured without using a ferromagnetic detector. These effects are measured both at room and low temperatures, and are suitable for their applications as nonlinear circuit elements in the fields of advanced spintronics and spin-based neuromorphic computing.