- Spin polarization
Spin polarization is the degree to which the spin, i.e. the intrinsic
angular momentum of elementary particles, is aligned with a given direction. This property may pertain to the spin, hence to themagnetic moment , ofconduction electrons in ferromagneticmetals , such asiron , giving rise to spin polarized currents. It may also pertain to beams of particles, produced for particular aims, such aspolarized neutron scattering ormuon spin spectroscopy . Spin polarization of electrons or of nuclei, often called simplymagnetization , is also produced by the application of amagnetic field , thanks to theCurie law and it is used to produce an induction signal inElectron spin resonance (ESR or EPR) and inNuclear magnetic resonance (NMR).Spin polarization is also important for
spintronics , a branch ofelectronics .Magnetic semiconductor s are being researched as possible spintronics materials.The spin of free electrons is measured either by a LEED image from a clean wolfram-crystal (SPLEED) or by an
electron microscope composed purely of electrostatic lenses and agold foil as a sample. Back scattered electrons are decelerated by annular optics and focused onto a ring shaped electron mulitplier at about 15°. The position on the ring is recorded. This whole device is called a Mott-detector. Depending on their spin the electrons have the chance to hit the ring at different positions. 1% of the electrons are scattered in the foil. Of these 1% are collected by the detector and then about 30% of the electrons hit the detector at the wrong position. Both devices work due to spin orbit coupling.
Wikimedia Foundation. 2010.