Spintronics-Info: the spintronics experts

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.

Researchers in the UK, South Korea and the U.S recently discovered that the two-dimensional layered magnet chromium triiodide (CrI₃) acts as a topological magnon insulator in the absence of an external magnetic field. This result could have potential applications for so-called dissipationless spintronics in which electrons are used to transmit and store information in an ultra-fast and ultra-low power fashion.

Thanks to detailed neutron scattering measurements and fine analysis, the team has found that this phenomenon comes from the way in which the layers in the material are stacked together. That is, while a single layer of CrI₃ is ferromagnetic, two stacked layers are antiferromagnetic which counterintuitively is different from that in ferromagnetic bulk.

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 collaboration, led by RMIT, has quantified spin in a 2D quantum spin Hall insulator (QSHI) WTe₂, a promising option for future low-energy nano-electronic and spintronic devices.

Using anisotropic magnetoresistance (AMR) to reveal the relationship between electrons’ spin and momentum, the team demonstrated the promising potential of QSHI for novel spintronic devices, and proved the value of AMR for design and development of QSHI-based spintronics.

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 at University of St. Andrews in the U.K., along with other institutes worldwide, have recently shown that helium can influence the spin polarization of the tunneling current and magnetic contrast of a technique known as spin-polarized scanning tunneling microscopy (SP STM). Their findings could have important implications for the development of new electronic devices.

In their previous research, the same research group investigated the magnetic order in the antiferromagnetic material iron telluride. They found that by collecting magnetic material from their sample's surface using an STM tip, they could image the sample's magnetic order.