Editing Spintronics (section)

=== Storage media ===
[[Antiferromagnetism|Antiferromagnetic]] storage media have been studied as an alternative to [[ferromagnetism]],<ref>{{cite web |author=Jungwirth, T. |type=announcement of a physics colloquium at a Bavarian university |date=28 April 2014 |title=Relativistic Approaches to Spintronics with Antiferromagnets |url=http://www.physik.uni-regensburg.de/aktuell/KollSS14/Kolloquium-Jungwirth.pdf |access-date=29 April 2014 |archive-date=29 April 2014 |archive-url=https://web.archive.org/web/20140429190040/http://www.physik.uni-regensburg.de/aktuell/KollSS14/Kolloquium-Jungwirth.pdf |url-status=dead }}</ref> especially since with antiferromagnetic material the bits can be stored as well as with ferromagnetic material. Instead of the usual definition 0&nbsp;↔ 'magnetisation upwards', 1&nbsp;↔ 'magnetisation downwards', the states can be, e.g., 0&nbsp;↔ 'vertically alternating spin configuration' and 1&nbsp;↔ 'horizontally-alternating spin configuration'.<ref>This corresponds mathematically to the transition from the rotation group SO(3) to its relativistic covering, the "double group" SU(2)</ref>).

The main advantages of antiferromagnetic material are:

* insensitivity to data-damaging perturbations by stray fields due to zero net external magnetization;<ref name=netzero>{{cite journal |last1=Jungwirth |first1=T. |last2=Marti |first2=X. |last3=Wadley |first3=P. |last4=Wunderlich |first4=J. |title=Antiferromagnetic spintronics |journal=Nature Nanotechnology |publisher=Springer Nature |volume=11 |issue=3 |year=2016 |issn=1748-3387 |doi=10.1038/nnano.2016.18 |pmid=26936817 |pages=231–241 |arxiv=1509.05296|bibcode=2016NatNa..11..231J |s2cid=5058124 }}</ref>
* no effect on near particles, implying that antiferromagnetic device elements would not magnetically disturb its neighboring elements;<ref name=netzero/>
* far shorter switching times (antiferromagnetic resonance frequency is in the THz range compared to GHz ferromagnetic resonance frequency);<ref name =adv>{{cite journal |last1=Gomonay |first1=O. |last2=Jungwirth |first2=T. |last3=Sinova |first3=J. |title=Concepts of antiferromagnetic spintronics |journal=Physica Status Solidi RRL |publisher=Wiley |volume=11 |issue=4 |date=21 February 2017 |issn=1862-6254 |doi=10.1002/pssr.201700022 |page=1700022 |arxiv=1701.06556|bibcode=2017PSSRR..1100022G |s2cid=73575617 }}</ref>
* broad range of commonly available antiferromagnetic materials including insulators, semiconductors, semimetals, metals, and superconductors.<ref name=adv/>

Research is being done into how to read and write information to antiferromagnetic spintronics as their net zero magnetization makes this difficult compared to conventional ferromagnetic spintronics. In modern MRAM, detection and manipulation of ferromagnetic order by magnetic fields has largely been abandoned in favor of more efficient and scalable reading and writing by electrical current. Methods of reading and writing information by current rather than fields are also being investigated in antiferromagnets as fields are ineffective anyway. Writing methods currently being investigated in antiferromagnets are through [[spin-transfer torque]] and [[Spin–orbit interaction|spin-orbit torque]] from the [[spin Hall effect]] and the [[Rashba effect]]. Reading information in antiferromagnets via magnetoresistance effects such as [[tunnel magnetoresistance]] is also being explored.<ref>{{cite journal |last1=Chappert |first1=Claude |last2=Fert |first2=Albert |last3=van Dau |first3=Frédéric Nguyen |title=The emergence of spin electronics in data storage |journal=Nature Materials |publisher=Springer Science and Business Media LLC |volume=6 |issue=11 |year=2007 |issn=1476-1122 |doi=10.1038/nmat2024 |pmid=17972936 |pages=813–823 |bibcode=2007NatMa...6..813C|s2cid=21075877 }}</ref>