Switching magnetization of nano-scale ferromagnetic particle using non-local spin injection

We have performed non-local spin injection into a nano-scale ferromagnetic particle configured in a lateral spin valve structure to switch its magnetization only by spin current. The non-local spin injection aligns the magnetization of the particle parallel to the magnetization of the spin injector. The responsible spin current for switching is estimated from the experiment to be about 200 $\mu$A, which is reasonable compared with the values obtained for conventional pillar structures. Interestingly the switching always occurs from anti-parallel to parallel in the particle/injector magnetic configurations, whereas no opposite switching is observed. Possible reasons for this discrepancy are discussed.