The magnetic moment is measured in Bohr Magneton (BM).Spin only magnetic moment of Fe in ${\left[\text{Fe}{\left({\text{H}}_2\text{O}\right)}_6\right]}^{3+}$ and ${\left[\text{Fe}{\left(\text{CN}\right)}_6\right]}^{3-}$ complexes respectively is:

Filed strength of ligand $\mathrm{CN}>{\mathrm{H}}_2\mathrm{O}{\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{+3}{\mathrm{Fe}}^{+3}\left[\mathrm{Ar}\right]{45}^{0}3{\mathrm{d}}^5$
No.of unpaired ${\mathrm{e}}^{-}=5\sqrt{\mathrm{n}(\mathrm{n}+2)}=\sqrt{5(5+2)}=5.92$$\left[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6\right]$

$\left[{\mathrm{Fe}}^{+3}\right]\left[\mathrm{Ar}\right]{45}^{0}3{\mathrm{d}}^5$
No.of unpaired ${\mathrm{e}}^{-}=1\sqrt{\mathrm{n}(\mathrm{n}+2)}=\sqrt{1(1+2)}=\sqrt{3}-1.73$