The ratio of magnetic moments of Fe (III) and Co (II) is 

$Fe\left(111\right)=\left[Ar\right]3d^{2}unpairedelectrons=5;$

            Magnetic moment $=\sqrt{5(5+2)};$

            Ratio = $\sqrt{7:}\sqrt{3}$

            Co(II) [Ar]  $3d^7$unpaired electrons = 3;

            Magnetic moment = $\sqrt{3(3+2)}$

            Ratio $\sqrt{7}:\sqrt{3}$