Magnetization reversal of permalloy film by pure spin current injection: relation between reversal time and injected surface

The dynamics of the magnetization reversal process in a nanosized permalloy film by the pure spin current (PSC) injection is analyzed. We have performed micromagnetic simulation based on the Landau-Lifshitz equation taking into account both the relaxation term and spin transfer torque term caused by the PSC. PSC is injected into the permalloy from a side of the film. We compare the magnetization reversal times among the PSCs injected from each of sides. The fast magnetization reversal occurs for the PSC injected from the side which area is smallest, i.e. highest spin current density, if we impose a condition that the intensity of the spin current is constant irrespective to the area of the side from which the PSC is injected.