spintronics otherwise magneto electronics (rus. спинтроника otherwise магнетоэлектроника; спиновая электроника) — a branch of solid state electronics based on the effect of spin-charge transport (spin-polarised transport).

Description

The field of science concerned with the study of the effects of interaction between intrinsic magnetic moments of electrons (spins) and electromagnetic fields, as well as with the application of these effects for developing so-called spin-electronic instruments and devices [1].

Two key components are needed for the creation of a spintronic device: a source of spin-polarised electrons (i.e., a source of electrons with mainly codirectional spins ) and a receiving system sensitive to the spin of polarised electrons (spin detector). Manipulations with electrons' spins in the process of transport between the source and the detector are realised by means of an external magnetic field or by means of effective fields created by spin-orbit interactions.

The easiest way to generate spin-polarised current is to pass current through a ferromagnetic material. A typical GMR-device (a device based on the giant magnetoresistance effect) consists of at least two layers of ferromagnetic material with a separating layer of conductive non-magnetic material. Electrical resistance is minimal when magnetisation vectors of ferromagnetic layers are parallel (respectively, the flowing current strength reaches its highest value), and current strength value is minimal in the case of oppositely directed magnetisation vectors. The operation of magnetic field sensors is based on this effect. It should be noted that the current generated in GMR-devices may flow both perpendicular and parallel to ferromagnetic layers. In addition to the GMR effect, spintronic devices can use other effects: tunnelling magnetoresistance (TMR) where the flow of electrons is created by their quantum-mechanical tunnelling through a thin insulating layer separating the ferromagnetic layers, or the spin torque transfer effect where the current of spin-polarised electrons is used to control the magnetisation vector of the device's ferromagnetic electrodes.

The most widely known and commonly used spintronic devices are hard drives. Recently, the use of magnetic sensors based on the GMR and TMR effects has significantly improved the sensitivity of reading heads which, in fact, measure the magnetic state of tiny magnetic domains (bits) on fast-spinning hard drives. Another well-known spintronic device is magnetic random access memory (MRAM) where polarised electrons are injected by means of magnetic quantum tunnelling. Such electron tunnel junctions between the two ferromagnetic layers are controllable. Each junction can store one bit of information which facilitates the creation of a new type of electronic semiconductor memory with high-speed writing and reading and high-density recording. Memory of this type ensures that information is preserved when power is off since this technology is based on magnetism (as opposed to electric charge in convenient types of memories); in addition, such memory does not require regeneration while in use [2,3].

Author

  • Razumovsky Alexey S.

Sources

  1. Awschalom D., Flatt´e M., Samarth N. Spintronics (Preview) // Scientific American Magazine. — www.scientificamerican.com/article.cfm?id=spintronics (reference date: 01.08.2010).
  2. Hoberman B. The Emergence of Practical MRAM // Crocus-technology. — http://www.crocus-technology.com/pdf/BH%20GSA%20Article.pdf (reference date: 01.08.2010).
  3. Spintronics Zhuvikin G. / / Computerra (in Russian). — http://offline.computerra.ru/2005/575/37385/ (reference date: 01.08.2010).

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