Spontaneous spin polarization

The f-band width was found to be about 5 eV in Ac, about 3 eV for Th-Np and around 2 eV for Pu. In Am it is down to 1 eV. The Stoner parameter, was calculated to be about 0.5 eV and almost constant throughout the series. At Am, however, the product I N(Ef) of the Stoner parameter and the f-density of states at the Fermi level exceeds one and spontaneous spin polarization occurs in the band calculation. Since Am has about 6.2 f-electrons and the moment saturates, this leads to an almost filled spin-up band and an empty spin-down band. The result is that the f-pressure all but vanishes leading to a large jump in atomic volume - in agreement with experiment. This has been interpreted as Mott-localization of the f-electrons at Am and the f-electrons of all actinides heavier than Am are Mott-localized. The trend in their atomic volumes is then similar to those of the rare earths. 

The work by Alvarado et al. [27] reports the observation of a spontaneous spin polarization of photoemitted electrons from GaAs (110) with linear polarization of the exciting light. As mentioned earlier (eq. 10) a spin up state in Fig. 10 has t as well as i components. For very small k only almost pure spin states will be found, but nevertheless photoemitted electrons which were excited to energies lying so close to the conduction band minimum will not exhibit a net polarization. Contributions from f... 

As has been alluded to by mentioning the electronic spin, an extension of density-functional theory to spin-density-functional theory is possible by simply decomposing the total electron density p(r) into the spin densities p r) and p (r) although there are some recent doubts as to the validity of the entire idea [149,150]. In practice, spin-DFT works very well. Spin-DFT is needed whenever the electrons feel an external magnetic field or are subject to spontaneous spin-polarization, such as in magnetic atoms, molecules, and solids (for example, itinerant magnets, see Section 3.5). Spin-DFT also allows different... 

The spontaneous spin-polarization also results in a rearrangement of the electron density in a-Fe, and the different energetic shifts of the a and jS spin... 

Fig. 86. Temperature dependences of the spontaneous muon spin precession iiequency (in the ferromagnetic state) and the muon spin relaxation rate (both in the ferromagnetic and paramagnetic states) in EuO. The data were analyzed with an exponential decay of muon spin polarization throughout. After Hartmann et al. (1996).

Researchers found that within picoseconds of absorbing an ultrashort laser pulse, electron spins in a semiconductor (GaAs) spontaneously polarize along the magnetization of a thin ferromagnetic layer, such as Iron (Fe), deposited on top of the GaAs. 

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