Spin filter

Spin-filter device is a magnetic tunnel junction using a ferromagnetic barrier, which can lead to highly spin-polarizaed current due to that one spin direction is filtered out from an unpolarized current effectively, because up- and down-spin electrons see different potential barrier heights to each other due to the exchange splitting of the ferromagnetic barrier. Namely, the electrons of one spin direction can tunnel through a ferromagnetic barrier much easier than the other spin direction electrons.

Fig. 1 Concept of MRAM.

Up to now spin-filtering devices have been reported with ferromagnetic semiconductor barriers, Eu calcogenides, in which the spin polarization reached up to 80% using a EuS barrier. Eu calcogenides, however, have a low Curie temperature, TC, thus, the spin filtering can not work at RT. The spin filtering devices which can operate at RT are strongly desired.