Spin-polarized current in ferromagnetic rod-to-film structure

Properties are discussed of a ferromagnetic junction of the type "rod contacting with film". Very high current density of the order of $10^9$ A/cm$^2$ may be achieved in the contact region. We show it can lead to inversion of population of the spin energy subbands. Spin injection depends strongly on the direction of the current (forward or backward). We prepared experimentally a rod-to-film structure and investigated high density current flowing through it. Current dependent radiation has been observed by means of a THz receiver. In particular, the radiation becomes different for forward and backward currents. It shows the radiation includes not only heating but also non-thermal (spin-injection) effects.