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'''Spin pumping''' is a method of generating a [[spin current]], the [[spintronics|spintronic]] analog of a [[battery (electricity)|battery]] in conventional [[electronics]].  

In order to make a spintronic device, the primary requirement is to have a system that can generate a current of spin-polarized [[electrons]], as well as a system that is sensitive to the spin polarization.  Most spintronic devices also have a unit in between these two that changes the current of electrons depending on the spin states. Candidates for such devices include injection schemes based on [[magnetic semiconductors]] and [[ferromagnetism|ferromagnetic]] [[metal]]s, [[ferromagnetic resonance]] devices<ref name=Tserkovnyak>
{{Cite journal 
 | title = Enhanced Gilbert Damping in Thin Ferromagnetic Films
 | year = 2002
 | volume = 88 | issue = 11
 | author = Y Tserkovnyak et al
 | journal = Physical Review Letters
 | doi = 10.1103/PhysRevLett.88.117601
 | bibcode=2002PhRvL..88k7601T
|arxiv = cond-mat/0110247 }}</ref>
, and a variety of [[spin-dependent pump]]s.  Optical, microwave and electrical methods are also being explored<ref>
 {{Cite journal 
 | title = Spin Pumping by Parametrically Excited Exchange Magnons
 | year = 2011
 | volume = 106 | page = 216601
 | author = C Sandweg et al
 | journal = Physical Review Letters
 | doi = 10.1103/PhysRevLett.106.216601
 | bibcode=2011PhRvL.106u6601S
|arxiv = 1103.2229 }}</ref>
.These devices could be used for low-power data transmission in [[spintronic]] devices<ref>
 {{Cite journal 
 | title = Spin-magnon transmutation
 | year = 2011
 | volume = 4 | page = 40
 | author = G E Bauer and Y Tserkovnyak
 | journal = Physics
 | doi = 10.1103/Physics.4.40
|bibcode = 2011PhyOJ...4...40B }}</ref>
or to transmit electrical signals through insulators.<ref>
 {{Cite journal 
 | title = Transmission of electrical signals by spin-wave interconversion in a magnetic insulator
 | year = 2010
 | volume = 464
 | author = Y Kajiwara
 | journal = Nature
 | doi = 10.1038/nature08876
 | issue=7286
|bibcode = 2010Natur.464..262K }}</ref>

The spin pumped into an adjacent layer by a precessing magnetic moment is given by<ref name=Tserkovnyak/>
:<math>\vec j_s = {\hbar \over {4 \pi}} g^{\uparrow \downarrow} {1 \over M_S^2} \langle \vec M(t) \times {{d \vec M(t))} \over {dt}} \rangle  </math>
where <math>\vec j_s</math> is the spin current (the vector indicates the orientation of the spin, ''not'' the direction of the current), <math>g^{\uparrow \downarrow}</math> is the spin-mixing conductance, <math> M_S^2</math> is the saturation magnetization, and <math>\vec M(t)</math> is the time-dependent orientation of the moment. 

==References==
{{Reflist}}

==See also==
*[[Spintronic]]
*[[Spin wave]]
*[[Spin Engineering]]
*[[Spin Hall effect]]

{{DEFAULTSORT:Spin Pumping}}
[[Category:Spintronics]]


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