Spin-polarised electrons can be generated in non-magnetic materials using the following methods: spin injection from a ferromagnet, a magnetic field, an electric field, electromagnetic wave introduction, Zeeman splitting, spin motive force, a thermal gradient and mechanical rotation. One of the most common methods is spin injection from a ferromagnetic material, e.g., conventional ferromagnetic metals (Fe, Co, Ni and Gd), half-metallic ferromagnets (HMF) and dilute magnetic semiconductors (DMS), attached to a non-magnetic metal or semiconductor through an ohmic contact or a tunnel barrier. A stray field at the edge of a ferromagnet can also be used to induce a population difference in spin-polarised electrons in a non-magnetic material. Electromagnetic wave, e.g., circularly polarised light excites spin-polarised electrons in a semiconductor, dependent upon an optical selection rule. The reverse effect generates circularly polarised light emission by a spin-polarised electron current. This can be extended further to spin generation by electromagnetic waves, including spin pumping and high-frequency spin induction. In addition a thermal gradient has been found to produce a spin-polarised carrier flow due to a spin Seebeck effect, which is useful for energy harvesting. This cluster also includes recent theoretical proposals on spin-generation by quantum geometrical effects and mechanical rotation.
|Frontiers in Physics
|Published - 14 Mar 2018