Why do compounds having similar geometry have different magnetic moment?

Explanation

It is due to the presence of weak or strong field ligands in complexes. If CFSE is high, the complex will show low value of magnetic moment and vice-cersa, e.g. `[CoF_(6)]^(3-)and[Co(NH_(3))_(6)]^(3+)`, the fromer is paramagnetic, and the latter is diamagnetic because `F^(-)` is a weak field ligand and `NH_(3)` is a strong field ligand while both have similar geometry.