Why is contribution of orbital motion to paramagnetism not quenched in lanthanoid ions. explain?

Lanthanoid ions are contracted when compared to the other ions. This is due to the vulnerability of the 4f electrons. The electrons are not shielded by other electrons which allow the nucleus to pull the electrons in the orbital closer. This is also the reason why the orbital motion's contribution to paramagnetism is not quenched in the ions.