May 2013

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 Spain have managed to create magnetic graphene, basically they developed a hybrid graphene surface that behaves like a magnet. This may enable graphene-based Spintronic devices.

The researchers grew a graphene sheet on a ruthernium single crystal substrate. Then they evaporated TCNQ (tetracyano-p-quinodimethane) molecules on the graphene surface. The TCNQ molecule acquired long-range magnetic order. While the graphene itself did not interact with the TCNQ molecules, it permitted a highly efficient charge transfer between the substrate (the ruthernium crystal) and the TCNQ.

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.

Beijing's Beihang University is hosting a "Spintronics based Computing" Workshop on May 22. The workshop will be hosted by Weisheng Zhao (from CNRS) and Zulin Wang (from Beihang University) and will include six lectures by speakers from China, the US and France, discussing topics such as "computing with embedded MRAM" and the "Design space exploration of STT-RAM cells".