Spin current - Page 5

Researchers NTU, NUS, A*STAR and the Los Alamos National Lab have demonstrated that it is possible to inject an ultra-short pulse of spin current (less than a picosecond) from a metal to a semiconductor in a very efficient way.

The researchers used a short laser pulse on cobalt (a magnetic material) - which generated a spin-polarized "swarm" of excited electrons. The spin-polarized electrons travel outside of the material - into adjacent materials. This creates an extremely efficient spin injection.

Researchers from the University of Utah developed two spintronics devices based on perovskite materials. The researchers use these new devices to demonstrate the high potential of perovksites for spintronics systems. This is a followup to the exciting results announced in 2017 by the same group that showed advantages of perovskites for spintronics.

The researchers use an organic-inorganic hybrid perovskite material that has a heavy lead atom that features strong spin-orbit coupling and a long injected spin lifetime.The first device is a spintronic LED which works with a magnetic electrode instead of an electron-hole electrode. The perovskite LED lights up with circularly polarized electroluminescence.

Researchers from Russia and Japan have shown, theoretically, that it is possible to create a new class of materials: spin-valley half-metals. These kind of devices could enable both spintronics valleytronics applications.

In "regular" half-metals, all the electrons that participate in electric currents have the same spin - and so the current is always spin-polarized. These materials have interesting applications for spintronics devices. In the new class of materials now proven theoretically to be possible, there are two valleys present - one providing electrons, one providing holes.

Researchers from Grennole Alpes University in France have demonstrated using atomistic calculations that a lateral electric field can be used to tune the carrier mobility and change the spin polarization of the current driving through zigzag graphene ribbons. The researchers say that these effects can be nicely exploited in spintronics devices.

The calculations predict a high variation of the carrier mobility, mean free path and spin polarization in the ZGNRs. It turns out that configurations with almost 100% spin-polarized current can be switched on and off.

The Johannes Gutenberg University Mainz (JGU), with funding from the German Research Foundation (DFG), is setting up an Emmy Noether independent junior research group to study spintronics.

Specifically, the TWIST (Topological Whirls in SpinTronics) work group will study skyrmions - magnetic "particles" or nodes within a magnetic texture. Skyrmions are more stable than other magnetic structures and react particularly readily to spin currents - which makes them interesting for spintronics applications.

Mark Stiles, from the NIST's Center for Nanoscale science and technology, gave an interesting lecture titled "Spin Current: the Torque Wrench of Spintronics" in which he discussed spintronics challenges, especially for spin-torque MRAM devices:

Researchers from TU Wien designed a method to create extremely strong spin currents using ultra-short laser pulses.

Using computer simulations, the researchers discovered that when short laser pulses hit a thin layer of nickel on a silicon substrate, the electrons accelerate toward the silicon, which builds an electric field on the interface of the two materials. This stops the current, but the spin is still transported. the spin-up electrons move freely, while the spin-down electrons have a much higher probability of being scattered at the nickel atoms. This creates many spin-up electrons in the silicon - effectively creating a spin current in the silicon.

Researchers from Japan and France managed to detect magnetic fluctuations with pure spin current. This has been done in a much more sensitive way than conventional magnetization measurements.

The researchers used spin glass, a typical frustrated system where a small amount of impurities with magnetic moments is randomly distributed in a nonmagnetic host metal. At high temperatures, the magnetic moments are fluctuating with a very high speed. As the temperature approaches the spin glass temperature (Tg), the fluctuations become slower and then the magnetic moments are frozen at Tg.

Researchers from the US DoE's Argonne National Laboratory discovered that a pure-spin current can be created in materials that are insulators. Previously it was thought that such a current is possible in magnetic materials only.

The researchers generated a magnetic field on a layer of ferromagnetic YIG (yttrium iron garnet) on a substrate of paramagnetic GGG (gadolinium gallium garnet). To their surprise, the spin current was stronger in the GGG than it was in the YIG. They actually do not know how this works - and understanding it is the next step in their research.

Researchers from the U.S. Naval Research Laboratory (NRL) developed a new type of room-temperature tunnel device structure in which the tunnel barrier and transport channel are both made of graphene.

In this new design, hydrogenated graphene acts as a tunnel barrier on another layer of graphene for charge and spin transport. The researchers demonstrated spin-polarized tunnel injection through the hydrogenated graphene, and lateral transport, precession and electrical detection of pure spin current in the graphene channel. The team sasy that the spin polarization values are higher than those found using more common oxide tunnel barriers, and spin transport at room temperature.