  We establish a general formalism of the bulk spin polarization (BSP) and the
current-based spin polarization (CSP) for mesoscopic ferromagnetic and
spin-orbit interaction (SOI) semiconducting systems. Based on this formalism,
we reveal the basic properties of BSP and CSP and their relationships. The BSP
describes the intrinsic spin polarized properties of devices. The CSP depends
on both intrinsic parameters of device and the incident current. For the
non-spin-polarized incident current with the inphase spin-phase coherence, CSP
equals to BSP. We give analytically the BSP and CSP of several typical
nanodevice models, ferromagnetic nanowire, Rashba nanowire and rings. These
results provide basic physical behaviors of BSP and CSP and their
relationships.

Mesoscale and Nanoscale Physics