1)The nuclear spin, the orientation of the nuclear spin ensemble with respect to the electron cloud, magnetic/quadrupole hyperfine interaction, …
2)At T=0, all nuclei will be in the lowest energy state m=+1, corresponding to an orientation along the positive z-axis. For slightly higher temperatures, some nuclei will be in the higher energy states m=0 and m=-1, but most of the nuclei will still be in the lowest energy level. This corresponds to a polarized nuclear ensemble orientation.