“…Spintronics, which focuses on using the spin state of electrons to store, carry and read information, has received a great deal of attention in recent years. 1–6 One of the major desirable goals of spintronics is to obtain pure spin current, 7 which is characterized by having the flow of spin angular-momentum without an accompanying charge current in the device. As both spin and charge are degrees of freedom for electrons and each flowing electron carries both charge current and spin current, pure spin currents can only be achieved when the same number of spin-up and spin-down electrons flow in opposite directions.…”