Magnetic semiconductor

See also: Bipolar magnetic semiconductor
Unsolved problem in physics:
Can we build materials that show properties of both ferromagnets and semiconductors at room temperature?
(more unsolved problems in physics)

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 (DMS) 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. They are of interest because of their unique spintronics properties with possible technological applications.[1][2] Doped wide band-gap metal oxides such as zinc oxide (ZnO) and titanium oxide (TiO2) are among the best candidates for industrial DMS due to their multifunctionality in opticomagnetic applications. In particular, ZnO-based DMS with properties such as transparency in visual region and piezoelectricity have generated huge interest among the scientific community as a strong candidate for the fabrication of spin transistors and spin-polarized light-emitting diodes,[3] while copper doped TiO2 in the anatase phase of this material has further been predicted to exhibit favorable dilute magnetism.[4]

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[5] and gallium arsenide[6] doped with manganese (the latter is commonly 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.

  1. ^ Furdyna, J.K. (1988). "Diluted magnetic semiconductors". J. Appl. Phys. 64 (4): R29. Bibcode:1988JAP....64...29F. doi:10.1063/1.341700.
  2. ^ Ohno, H. (1998). "Making Nonmagnetic Semiconductors Ferromagnetic". Science. 281 (5379): 951–5. Bibcode:1998Sci...281..951O. doi:10.1126/science.281.5379.951. PMID 9703503.
  3. ^ Ogale, S.B (2010). "Dilute doping, defects, and ferromagnetism in metal oxide systems". Advanced Materials. 22 (29): 3125–3155. Bibcode:2010AdM....22.3125O. doi:10.1002/adma.200903891. PMID 20535732. S2CID 25307693.
  4. ^ Assadi, M.H.N; Hanaor, D.A.H (2013). "Theoretical study on copper's energetics and magnetism in TiO2 polymorphs". Journal of Applied Physics. 113 (23): 233913–233913–5. arXiv:1304.1854. Bibcode:2013JAP...113w3913A. doi:10.1063/1.4811539. S2CID 94599250.
  5. ^ Munekata, H.; Ohno, H.; von Molnar, S.; Segmüller, Armin; Chang, L. L.; Esaki, L. (1989-10-23). "Diluted magnetic III-V semiconductors". Physical Review Letters. 63 (17): 1849–1852. Bibcode:1989PhRvL..63.1849M. doi:10.1103/PhysRevLett.63.1849. ISSN 0031-9007. PMID 10040689.
  6. ^ Ohno, H.; Shen, A.; Matsukura, F.; Oiwa, A.; Endo, A.; Katsumoto, S.; Iye, Y. (1996-07-15). "(Ga,Mn)As: A new diluted magnetic semiconductor based on GaAs". Applied Physics Letters. 69 (3): 363–365. Bibcode:1996ApPhL..69..363O. doi:10.1063/1.118061. ISSN 0003-6951.