  Out-of-plane spin polarization {\sigma}_z has attracted increasing interests
of researchers recently, due to its potential in high-density and low-power
spintronic devices. Noncollinear antiferromagnet (AFM), which has unique
120{\deg} triangular spin configuration, has been discovered to possess
{\sigma}_z. However, the physical origin of {\sigma}_z in noncollinear AFM is
still not clear, and the external magnetic field-free switching of
perpendicular magnetic layer using the corresponding {\sigma}_z has not been
reported yet. Here, we use the cluster magnetic octupole in antiperovskite AFM
Mn3SnN to demonstrate the generation of {\sigma}_z. {\sigma}_z is induced by
the precession of carrier spins when currents flow through the cluster magnetic
octupole, which also relies on the direction of the cluster magnetic octupole
in conjunction with the applied current. With the aid of {\sigma}_z, current
induced spin-orbit torque (SOT) switching of adjacent perpendicular ferromagnet
is realized without external magnetic field. Our findings present a new
perspective to the generation of out-of-plane spin polarizations via
noncollinear AFM spin structure, and provide a potential path to realize
ultrafast high-density applications.
