Local off-cubic distortion the cause for the low- and high-spin states   of the Co3+ ion
  It is pointed out that it is the local symmetry that determines the realization of the low- and high-spin state of the Co3+ ion. We can rigorously prove it treating the Co3+ ion as the highly-correlated electron system 3d6, that fulfiles the Hund's rules with taking into account the spin-orbit coupling. As the function of the sign of the off-cubic crystal-field distortion the magnetic or non-magnetic state is realized. 
R.J. Radwanski, Z.Ropka