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

TL;DR

This paper investigates a ferromagnetic rod-to-film structure that achieves extremely high current densities, leading to spin population inversion and spin-dependent radiation, with experimental evidence of non-thermal effects.

Contribution

It presents the first experimental demonstration of high-density current-induced spin population inversion and spin-dependent THz radiation in a rod-to-film ferromagnetic structure.

Findings

Achieved current densities of about 10^9 A/cm^2 in the contact region.

Observed current-dependent THz radiation with different characteristics for forward and backward currents.

Provided evidence of non-thermal spin-injection effects beyond heating.

Abstract

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.