Bulk magnetization (Mo)

Mo

y

x

z

x

y

z

Bo

Bo

Now consider a real sample containing numerous nuclear spins:

Mo % (Na - Nb)

m   =   mxi + myj +mzk

Since m is precessing in the xy-plane, Mo = ∑ mzk – m-zk

m is quantized (a or b), Mo has a continuous number of states, bulk property.