A spin current carries spin angular momentum in a spintronics device. Its interaction with a magnetic nanostructure not only gives rise to spin-dependent transport but also excites dynamics in the magnetic state. Unlike the spin-polarized electrical current, a pure spin current is useful for both fundamental and applied research because neither Oersted fields nor electrical current-related spurious effects are produced. Nonlocal electrical spin injection is a feasible way to produce the pure spin current. Here we demonstrate that the nonlocal spin valve signal is increased by an order of magnitude by improving the interface quality in a new device structure using a clean, in situ fabrication process. The generated pure spin current enables the magnetization reversal of a nanomagnet as efficiently as electrical current-induced magnetization switching. These results will open the door towards the realization of a pure-spin-current-driven device.