Thickness-Dependent Self-Induced Spin-Pumping in Cobalt Thin Films

A spin current can be produced and converted into a charge current in a single ferromagnetic material layer. Such an effect is called self-induced spin pumping. It is usually ignored in the bilayer structures. However, it is very important in application of the single layer structure. In this paper, the inverse spin Hall effect (ISHE) induced voltage in a series of single layered cobalt (Co) thin films with various thicknesses is investigated. The Co thin films are prepared by the magnetron sputtering system. The quantitative analysis of charge current density ( j
_c
), effective magnetization (4πM
_eff
), and damping constant (α) is obtained by analyzing the ISHE and ferromagnetic resonance data. Both the charge current and damping constant are thickness-dependent. The calculated values of j
_c
have a linear dependence on (1/α
²
), consistent with the theory of spin pumping.