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Magnetic semiconductor
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<h2 id="theory">Theory</h2> <p>The pioneering work of Dietl <i>et al.</i> showed that a modified Zener model for magnetism<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> well describes the carrier dependence, as well as anisotropic properties of <a href="/facts/GaMnAs/r8LE1eI2">GaMnAs</a>. The same theory also predicted that room-temperature <a href="/facts/Ferromagnetism/fH3HFnSl">ferromagnetism</a> should exist in heavily <a href="/facts/P-type_semiconductor/d9GPL5tV">p-type</a> <a href="/facts/Doping_(semiconductors)/WrGdtWnm">doped</a> ZnO and GaN doped by Co and Mn, respectively. These predictions were followed of a flurry of theoretical and experimental studies of various oxide and nitride semiconductors, which apparently seemed to confirm room temperature ferromagnetism in nearly any semiconductor or insulator material heavily doped by <a href="/facts/Transition_metal/0slGWoLQ">transition metal</a> impurities. However, early <a href="/facts/Density_functional_theory/wwz4Gqdg">Density functional theory</a> (DFT) studies were clouded by band gap errors and overly delocalized defect levels, and more advanced DFT studies refute most of the previous predictions of ferromagnetism.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> Likewise, it has been shown that for most of the oxide based materials studies for magnetic semiconductors do not exhibit an intrinsic <i>carrier-mediated</i> ferromagnetism as postulated by Dietl <i>et al.</i><a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> To date, <a href="/facts/GaMnAs/r8LE1eI2">GaMnAs</a> remains the only semiconductor material with robust coexistence of ferromagnetism persisting up to rather high Curie temperatures around 100–200 K. </p> <h2 id="materials">Materials</h2> <p>The manufacturability of the materials depend on the thermal equilibrium <a href="/facts/Solubility/kLE9h3Jb">solubility</a> of the <a href="/facts/Dopant/DvChmeRL">dopant</a> in the base material. E.g., solubility of many dopants in <a href="/facts/Zinc_oxide/P7sTyDez">zinc oxide</a> 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 <a href="/facts/Thin_film/nSeoUT4Q">thin films</a>. </p><p>Permanent magnetization has been observed in a wide range of semiconductor based materials. Some of them exhibit a clear correlation between <a href="/facts/Carrier_density/vvzQRhL7">carrier density</a> and magnetization, including the work of T. Story and co-workers where they demonstrated that the ferromagnetic Curie temperature of <a href="/facts/Manganese/j9ELd1TL">Mn2+</a>-doped <a href="/facts/Lead_tin_telluride/WAxevCSa">Pb1−xSnxTe</a> can be controlled by the <a href="/facts/Carrier_density/vvzQRhL7">carrier concentration</a>.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> The theory proposed by Dietl required <a href="/facts/Charge_carriers_in_semiconductors/wpjjql4x">charge carriers</a> in the case of <a href="/facts/Electron_hole/YymdTv9d">holes</a> to mediate the <a href="/facts/Magnetic_coupling/3F785Xec">magnetic coupling</a> of manganese <a href="/facts/Dopant/DvChmeRL">dopants</a> in the prototypical magnetic semiconductor, Mn2+-doped <a href="/facts/GaAs/BakLFjpp">GaAs</a>. If there is an insufficient hole concentration in the magnetic semiconductor, then the <a href="/facts/Curie_temperature/ygotSuMg">Curie temperature</a> would be very low or would exhibit only <a href="/facts/Paramagnetism/vj1SMbbp">paramagnetism</a>. However, if the hole concentration is high (>~1020 cm−3), then the <a href="/facts/Curie_temperature/ygotSuMg">Curie temperature</a> would be higher, between 100 and 200 K. <a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> However, many of the semiconductor materials studied exhibit a permanent magnetization <i>extrinsic</i> to the semiconductor host material.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> A lot of the elusive extrinsic ferromagnetism (or <i>phantom ferromagnetism</i>) is observed in thin films or nanostructured materials.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p><p>Several examples of proposed ferromagnetic semiconductor materials are listed below. Notice that many of the observations and/or predictions below remain heavily debated. </p> <ul><li><a href="/facts/Manganese/j9ELd1TL">Manganese</a>-doped <a href="/facts/Indium_arsenide/GMhtPVbU">indium arsenide</a> and <a href="/facts/Gallium_arsenide/BakLFjpp">gallium arsenide</a> (<a href="/facts/GaMnAs/r8LE1eI2">GaMnAs</a>), with Curie temperature around 50–100 K and 100–200 K, respectively</li> <li>Manganese-doped <a href="/facts/Indium_antimonide/76EPwVLC">indium antimonide</a>, which becomes ferromagnetic even at room temperature and even with less than 1% Mn.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a></li> <li>Oxide semiconductors<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> <ul><li>Manganese- and <a href="/facts/Iron/QK1JYy8E">iron</a>-doped <a href="/facts/Indium_oxide/S5wHB48A">indium oxide</a>, ferromagnetic at room temperature. The ferromagnetism appears to be mediated by carrier-electrons,<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a><a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> in a similar way as the <a href="/facts/GaMnAs/r8LE1eI2">GaMnAs</a> ferromagnetism is mediated by carrier-holes.</li> <li><a href="/facts/Zinc_oxide/P7sTyDez">Zinc oxide</a> <ul><li>Manganese-doped <a href="/facts/Zinc_oxide/P7sTyDez">zinc oxide</a></li> <li><a href="/facts/N-type_semiconductor/d9GPL5tV">n-type</a> cobalt-doped <a href="/facts/Zinc_oxide/P7sTyDez">zinc oxide</a><a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a><a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a></li></ul></li> <li><a href="/facts/Magnesium_oxide/0GfLn47t">Magnesium oxide</a>: <ul><li><a href="/facts/P-type_semiconductor/d9GPL5tV">p-type</a> transparent MgO films with cation vacancies,<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a><a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a> combining ferromagnetism and multilevel switching (<a href="/facts/Memristor/BrFKeE7l">memristor</a>)</li></ul></li> <li><a href="/facts/Titanium_dioxide/T0KWmKcz">Titanium dioxide</a>: <ul><li><a href="/facts/Cobalt/gqhScEw4">Cobalt</a>-doped <a href="/facts/Titanium_dioxide/T0KWmKcz">titanium dioxide</a> (both <a href="/facts/Rutile/qwJH5ElN">rutile</a> and <a href="/facts/Anatase/wD932gCW">anatase</a>), ferromagnetic above 400 <a href="/facts/Kelvin/E3trzC4C">K</a></li> <li><a href="/facts/Chromium/6sVk6Uu7">Chromium</a>-doped <a href="/facts/Rutile/qwJH5ElN">rutile</a>, ferromagnetic above 400 <a href="/facts/Kelvin/E3trzC4C">K</a></li> <li><a href="/facts/Iron/QK1JYy8E">Iron</a>-doped rutile and iron-doped anatase, ferromagnetic at room temperature</li> <li><a href="/facts/Copper/I8PEE8oX">Copper</a>-doped <a href="/facts/Anatase/wD932gCW">anatase</a><a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a></li> <li><a href="/facts/Nickel/KwMCHYRP">Nickel</a>-doped <a href="/facts/Anatase/wD932gCW">anatase</a></li></ul></li> <li><a href="/facts/Tin_dioxide/tLGukNFB">Tin dioxide</a> <ul><li>Manganese-doped <a href="/facts/Tin_dioxide/tLGukNFB">tin dioxide</a>, with Curie temperature at 340 K</li> <li>Iron-doped <a href="/facts/Tin_dioxide/tLGukNFB">tin dioxide</a>, with Curie temperature at 340 K</li> <li>Strontium-doped tin dioxide (SrSnO2) – Dilute magnetic semiconductor. Can be synthesized an <a href="/facts/Epitaxial/etjSn1D3">epitaxial</a> thin film on a silicon chip.<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a><a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a></li></ul></li> <li><a href="/facts/Europium(II)_oxide/geBHrbN2">Europium(II) oxide</a>, with a Curie temperature of 69K. The curie temperature can be more than doubled by doping (e.g. oxygen deficiency, Gd).</li></ul></li> <li><a href="/facts/Nitride/9vkrCbJ4">Nitride</a> semiconductors <ul><li>Chromium doped <a href="/facts/Aluminium_nitride/CkEzMbrM">aluminium nitride</a><a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a></li></ul></li> <li>(Ba,K)(Zn,Mn)2As2: Ferromagnetic semiconductor with tetragonal average structure and orthorhombic local structure.<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a></li></ul> <h2 id="external-links">External links</h2> <ul><li>Cabot, Andreu; Puntes, Victor F.; Shevchenko, Elena; Yin, Yadong; Balcells, Lluís; Marcus, Matthew A.; Hughes, Steven M.; Alivisatos, A. Paul (2007). <a href="https://web.archive.org/web/20120301074019/http://xraysweb.lbl.gov/uxas/Publicatons/Papers/pdfs/cabot%20FeNanos.pdf">"Vacancy Coalescence during Oxidation of Iron Nanoparticles"</a> (PDF). <i>Journal of the American Chemical Society</i>. 129 (34): 10358–10360. <a href="/facts/Bibcode_(identifier)/9HtdQSGB">Bibcode</a>:<a href="https://ui.adsabs.harvard.edu/abs/2007JAChS.12910358C">2007JAChS.12910358C</a>. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1021%2Fja072574a">10.1021/ja072574a</a>. <a href="/facts/PMID_(identifier)/JlHAvMHt">PMID</a> <a href="https://pubmed.ncbi.nlm.nih.gov/17676738">17676738</a>. <a href="/facts/S2CID_(identifier)/ldJsHa2Y">S2CID</a> <a href="https://api.semanticscholar.org/CorpusID:13430331">13430331</a>. Archived from <a href="http://xraysweb.lbl.gov/uxas/Publicatons/Papers/pdfs/cabot%20FeNanos.pdf">the original</a> (PDF) on 2012-03-01. Retrieved 2009-11-20.</li> <li>Chambers, Scott A. (2010). <a href="https://doi.org/10.1002%2Fadma.200901867">"Epitaxial Growth and Properties of Doped Transition Metal and Complex Oxide Films"</a>. <i>Advanced Materials</i>. 22 (2): 219–248. <a href="/facts/Bibcode_(identifier)/9HtdQSGB">Bibcode</a>:<a href="https://ui.adsabs.harvard.edu/abs/2010AdM....22..219C">2010AdM....22..219C</a>. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1002%2Fadma.200901867">10.1002/adma.200901867</a>. <a href="/facts/PMID_(identifier)/JlHAvMHt">PMID</a> <a href="https://pubmed.ncbi.nlm.nih.gov/20217685">20217685</a>. <a href="/facts/S2CID_(identifier)/ldJsHa2Y">S2CID</a> <a href="https://api.semanticscholar.org/CorpusID:5415994">5415994</a>.</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Furdyna, J.K. (1988). "Diluted magnetic semiconductors". J. Appl. Phys. 64 (4): R29. 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