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.
Researchers from Japan's Kyoto University and Osaka University have demonstrated that spin currents can travel more than half a micrometer on a thin doped-germanium sheet. Up until now this has only been demonstrated in very low temperatures (below 225 Kelvin).
Germanium has a higher electron mobility than silicon and a particular lattice symmetry that should reduce much of the electrons spin relaxation. But the material is not magnetic and so measuring spin transport is not easy because spin currents have to be created in a magnetic material and injected into germanium.
Researchers from Tohoku University and the Japan Science and Technology Agency (JST) have confirmed that surface plasmon resonance can be used to generate spin currents.
Surface plasmon resonance happens when electrons are hit by photos and react by vibrating. It is commonly used in bio-sensors and lab-on-a-chop systems. The researchers have shown that directing light on a certain magnetic material, a spin current can be produced and controlled.
Researchers from the US Naval Research Laboratory (NRL) developed a new type of tunnel device structure in which both the tunnel barrier and transport channel are made from graphene. The researchers say that this device features the highest spin injection values yet measured for graphene, and this design could pave they way towards highly functional and scalable graphene electronic and spintronic devices.
The tunnel barrier is made from dilutely fluorinated graphene while the charge and transport layer is made from graphene. The researcher demonstrated tunnel injection through the fluorinated graphene, and lateral transport and electrical detection of pure spin current in the graphene channel.
Researchers from Tohoku Univeristy generated a new kind of magnetoresistance in a system with an insulating magnet. They call this new phenomenon Spin Hall magnetoresistance (SMR). In SMR, the current does not need to pass through a magnet. The researchers developed a system in which a normal metal is put in contact with a magnetic insulator. The resistance of the normal metal is influenced by the magnetization in the insulating magnet even though none of the charge current is able to pass through the magnet.
The SMR effect is a result of spin current being able to flow from the metal into the magnetic insulator. The rate of this spin transfer depends on the magnetization direction of the insulator. The more spin current passing across the metal-insulator interface, the weaker the charge current flowing through the metal.
Researchers from the University of Delaware confirmed that electrons generate a magnetic field. In materials made from two layers of a heavy metal and a ferromagnetic material, the spin current diffuses into the ferromagnetic material. When this happens, a magnetic field is generated.
This magnetic field does not radiate beyond the ferromagnetic material (unlike regular magnetic fields). This is important in applications such as MRAM in which shielding the magnetic fields between memory cells is difficult. If devices use the new magnetic field it may be easier to create high density MRAM cells or other devices.