Research / Technical - Page 12

A research team led by Prof. Kim Jun Sung in the Center for Artificial Low Dimensional Electron Systems within the Institute for Basic Science (IBS, South Korea) and Physics Department at Pohang University of Science and Technology (POSTECH, South Korea) has found a new magnetotransport phenomenon, in the magnetic semiconductor Mn₃Si₂Te₆. The group found that the magnitude of change in resistance can reach as much as a billion-fold under a rotating magnetic field. This unprecedented shift of resistance depending on magnetic field angle is called colossal angular magnetoresistance (CAMR).

A key challenge in spintronics is finding an efficient and sensitive way to electrically detect the electronic spin state. For example, the discovery of giant magnetoresistance (GMR) in the late 1980s, allowed for such functionality. In GMR, a large change in electrical resistance occurs under the magnetic field depending on parallel or antiparallel spin configurations of the ferromagnetic bilayer. The discovery of GMR has led to the development of hard-disk drive technology, which is technically the first-ever mass-produced spintronic device. Since then, discoveries of other related phenomena, including colossal magnetoresistance (CMR) which occurs in the presence of a magnetic field, have advanced our understanding of the interplay between spin and charge degrees of freedom and served as a foundation of emergent spintronic applications.

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.

Scientists at the University of Wisconsin-Madison have developed an all-thin-film membrane composite of the relaxor-ferroelectric material lead magnesium niobate-lead titanate (PMN-PT) and ferromagnetic nickel that demonstrates an intrinsic coupling between voltage and spin.

When they apply voltage to the structure, it rotates the spins of the nickel layer, a magnetoelectric effect important for spintronics. The extreme thinness of the structure allows the use of low-voltages.

An international team of scientists from Austria and Germany has launched a new paradigm in magnetism and superconductivity, highlighting the effects of curvature, topology, and 3D geometry.

In modern magnetism, superconductivity and spintronics, extending nanostructures into the third dimension has become a major research avenue because of geometry-, curvature- and topology-induced phenomena. This approach provides a means to improve this and to launch novel functionalities by tailoring the curvature and 3D shape.

Researchers from Japan's Tokyo Institute of Technology, National Institute for Materials Science and National Institute of Advanced Industrial Science and Technology have found that lead-based vacancy centers in diamonds, that form after high-pressure and high-temperature treatment, are ideal for quantum networks, spintronics and quantum sensors.

The color in a diamond comes from a defect, or “vacancy,” where there is a missing carbon atom in the crystal lattice. Vacancies have long been of interest to electronics researchers because they can be used as ‘quantum nodes’ or points that make up a quantum network for the transfer of data. One of the ways of introducing a defect into a diamond is by implanting it with other elements, like nitrogen, silicon, or tin. In their recent study, the scientists from Japan demonstrated that lead-vacancy centers in diamond have the right properties to function as quantum nodes. “The use of a heavy group IV atom like lead is a simple strategy to realize superior spin properties at increased temperatures, but previous studies have not been consistent in determining the optical properties of lead-vacancy centers accurately,” says Associate Professor Takayuki Iwasaki of Tokyo Institute of Technology (Tokyo Tech), who led the study.

The attractive properties of Sr₂RuO₄, like its ability to carry lossless electrical currents and magnetic information simultaneously, make it a material with great potential for the development of future technologies like superconducting spintronics and quantum electronics. An international research team, led by scientists at the University of Konstanz, was recently able to answer one of the most interesting open questions on Sr₂RuO₄: why does the superconducting state of this material exhibit some features that are typically found in materials known as ferromagnets, which are considered being antagonists to superconductors?

Spin polarized muon particles (red spheres with arrows) probing a new form of magnetism in the perovskite superconductor Sr2RuO4. Credit: Konstanz University

The team has found that the material hosts a new form of magnetism, which can coexist with superconductivity and exists independently of superconductivity as well.

Scientists from Australia's Monash University (affiliated with Fleet, the Australian research council funded ‘Arc Centre of Excellence in Future low-energy Electronics Technologies’) have discovered how magnetism occurs in 2D ‘kagome’ metal-organic frameworks, opening the door to self-assembling controllable nano-scale electronic and spintronic devices.

Kagome materials have repeating patterns of hexagons and smaller triangles, with the hexagons touching at their tips. The word 'Kagome' comes from Japanese, relating to a basket weaving pattern.

Rice University researchers have confirmed the topological origins of magnons, magnetic features they discovered three years ago in a 2D material that could prove useful for encoding information in the spins of electrons.

The discovery provides a new understanding of topology-driven spin excitations in materials known as 2D van der Waals magnets. The materials are of growing interest for spintronics - for computation, storage and communications.

An international team of researchers has presented a finding that could help to identify exotic quantum states. The team seen strongly competing factors that affect an electron's behavior in a high-quality quantum material.

As an electron moves, its motion and spin can become linked through an effect known as spin–orbit coupling. This effect is useful because it offers a way to externally control the motion of an electron depending on its spin—a vital ability for spintronics. Spin–orbit coupling is a complex mix of quantum physics and relativity, but it becomes easier to understand by envisioning a round soccer ball. "If a soccer player kicks the ball, it flies on a straight trajectory," explains Denis Maryenko of the RIKEN Center for Emergent Matter Science. "But if the player gives the ball some rotation, or spin, its path bends." The ball's trajectory and its spinning motion are connected. If its spinning direction is reversed, the ball's path will bend in the opposite direction.

Researchers from Daegu Gyeongbuk Institute of Science and Technology (DGIST) in Korea have demonstrated a novel route to tune and control the magnetic domain wall motions employing combinations of useful magnetic effects inside very thin film materials. The research offers a new insight into spintronics and a step towards new ultrafast, ultrasmall, and power-efficient IT devices.

The new study demonstrates a new way to handle information processing using the movement of the magnetic states of the thin film device. It takes advantage of some unusual effects that occur when materials with contrasting types of magnetic material are squashed together. The research focuses on a device that combines ferromagnetic and antiferromagnetic materials, in which the directions of electron spins align differently within the respective magnetic materials.