Magnetic semiconductor

Magnetic semiconductor

Magnetic semiconductors are semiconductor materials that exhibit both ferromagnetism (or a similar response) and useful semiconductor properties. If implemented in devices, these materials could provide a new type of control of conduction. Whereas traditional electronics are based on control of charge carriers (n- or p-type), practical magnetic semiconductors would also allow control of quantum spin state (up or down). This would theoretically provide near-total spin polarization (as opposed to iron and other metals, which provide only ~50% polarization), which is an important property for spintronics applications, e.g. spin transistors.

While many traditional magnetic materials, such as magnetite, are also semiconductors (magnetite is a semimetal semiconductor with bandgap 0.14 eV), materials scientists generally predict that magnetic semiconductors will only find widespread use if they are similar to well-developed semiconductor materials. To that end, dilute magnetic semiconductors have recently been a major focus of magnetic semiconductor research. These are based on traditional semiconductors, but are doped with transition metals instead of, or in addition to, electronically active elements.

Hideo Ohno and his group at the Tohoku University were the first to measure ferromagnetism in transition metal doped compound semiconductors such as indium arsenide and gallium arsenide doped with manganese referred to as GaMnAs. These materials exhibited reasonably high Curie temperatures (yet below room temperature) that scales with the concentration of p-type charge carriers. Ever since, ferromagnetic signals have been measured from various semiconductor hosts doped with different transition atoms.


The manufacturability of the materials depend on the thermal equilibrium solubility of the dopant in the base material. E.g., solubility of many dopants in zinc oxide is high enough to prepare the materials in bulk, while some other materials have so low solubility of dopants that to prepare them with high enough dopant concentration thermal nonequilibrium preparation mechanisms have to be employed, e.g. growth of thin films.

A flurry of research in the past few years has shed some light on the crucial factors that are needed to achieve high-Curie temperature (above room temperature) ferromagnetic semiconductors, which can explain the so-called controversy in the field and lack of reproducibility in the magnetic properties for the same materials. Indeed, the first great discovery in the field was in 1986 by T. Story and co-workers where they demonstrated that the ferromagnetic Curie temperature of Mn2+-doped carrier concentration.[1] The theory proposed by Dietl required charge carriers in the case of holes to mediate the magnetic coupling of manganese dopants in the prototypical magnetic semiconductor, Mn2+-doped GaAs. If there is an insufficient hole concentration in the magnetic semiconductor, then the Curie temperature would be very low or would exhibit only paramagnetism. However, if the hole concentration is high (>~1020 cm−3), then the Curie temperature would be higher, between 100-200 K.[2]

Recent research by the University of Washington group led by Daniel Gamelin has shed some light for instance on the importance of interstitial zinc (a shallow donor) for controlling the ferromagnetism in a high-Curie temperature, Co2+-doped ZnO.[3][4]

Several examples of ferromagnetic semiconductor materials are e.g.:

External links

  1. ^ Story, T.; Gała̧zka, R.; Frankel, R.; Wolff, P. (1986). "Carrier-concentration–induced ferromagnetism in PbSnMnTe". Physical Review Letters 56 (7): 777. Bibcode 1986PhRvL..56..777S. doi:10.1103/PhysRevLett.56.777. 
  2. ^ Dietl, T.; Ohno, H; Matsukura, F; Cibert, J; Ferrand, D (2000). "Zener Model Description of Ferromagnetism in Zinc-Blende Magnetic Semiconductors". Science 287 (5455): 1019–1022. Bibcode 2000Sci...287.1019D. doi:10.1126/science.287.5455.1019. PMID 10669409. 
  3. ^ a b Kittilstved, Kevin; Schwartz, Dana; Tuan, Allan; Heald, Steve; Chambers, Scott; Gamelin, Daniel (2006). "Direct Kinetic Correlation of Carriers and Ferromagnetism in Co2+:  ZnO". Physical Review Letters 97 (3). Bibcode 2006PhRvL..97c7203K. doi:10.1103/PhysRevLett.97.037203. 
  4. ^ "Technology". BBC News. 2006-08-09. Retrieved 2010-09-19. 
  5. ^ "Muons in Magnetic Semiconductors". Retrieved 2010-09-19. 
  6. ^ Fukumura, T; Toyosaki, H; Yamada, Y (2005). "Magnetic oxide semiconductors". Semiconductor Science and Technology 20 (4): S103–S111. arXiv:cond-mat/0504168. Bibcode 2005SeScT..20S.103F. doi:10.1088/0268-1242/20/4/012. 
  7. ^ Chambers, Scott A. (2010). "Epitaxial Growth and Properties of Doped Transition Metal and Complex Oxide Films". Advanced Materials 22 (2): 219–248. doi:10.1002/adma.200901867. PMID 20217685. 

Wikimedia Foundation. 2010.

Игры ⚽ Нужно сделать НИР?

Look at other dictionaries:

  • magnetic semiconductor — magnetinis puslaidininkis statusas T sritis automatika atitikmenys: angl. magnetic semiconductor vok. magnetischer Halbleiter, m rus. магнитный полупроводник, m pranc. semi conducteur magnétique, m …   Automatikos terminų žodynas

  • Semiconductor device — Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium, and gallium arsenide. Semiconductor devices have replaced thermionic devices (vacuum tubes) in most …   Wikipedia

  • Magnetic core memory — Magnetic core memory, or ferrite core memory, is an early form of random access computer memory. It uses small magnetic ceramic rings, the cores , through which wires are threaded to store information via the polarity of the magnetic field they… …   Wikipedia

  • Magnetic-core memory — A 32 x 32 core memory plane storing 1024 bits of data. Computer memory types Volatile RAM DRAM (e.g., DDR SDRAM) SRA …   Wikipedia

  • semiconductor device — ▪ electronics Introduction       electronic circuit component made from a material that is neither a good conductor nor a good insulator (hence semiconductor). Such devices have found wide applications because of their compactness, reliability,… …   Universalium

  • semiconductor — /sem ee keuhn duk teuhr, sem uy /, n. 1. a substance, as silicon or germanium, with electrical conductivity intermediate between that of an insulator and a conductor: a basic component of various kinds of electronic circuit element (semiconductor …   Universalium

  • Magnetic amplifier — The magnetic amplifier (colloquially known as a mag amp ) is an electromagnetic device for amplifying electrical signals. The magnetic amplifier was invented early in the 20th century, and was used as an alternative to vacuum tube amplifiers… …   Wikipedia

  • magnetic ceramics — Introduction       oxide materials that exhibit a certain type of permanent magnetization called ferrimagnetism. Commercially prepared magnetic ceramics are used in a variety of permanent magnet, transformer, telecommunications, and information… …   Universalium

  • Semiconductor memory — Computer memory types Volatile RAM DRAM (e.g., DDR SDRAM) SRAM In development T RAM Z RAM TTRAM Historical Delay line memory Selectron tube Williams tube Non volatile …   Wikipedia

  • magnetic core — noun (computer science) a tiny ferrite toroid formerly used in a random access memory to store one bit of data; now superseded by semiconductor memories each core has three wires passing through it, providing the means to select and detect the… …   Useful english dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”