Phenomenological Description of Spin Coulomb Drag Considering Spin-Flip Possibility

The phenomenological equations for spin coulomb drag using the spin-drag co-efficient γ is discussed in this paper. Expression for transresistivity ρ is also given and it is shown that γ is directly proportional to ρ. In brief electron-electron collision and electron-impurity collision with spin-flip process are discussed. Finally, the collision-integral equation is given which interprets spin coulomb drag as damping mechanism for spin-current and a source for power loss in spintronic devices or circuits.