The correct order of the magnetic moment is:

$\left[{ }_{25}\mathrm{Mn}{,}_{24}\mathrm{Cr}{,}_{26}\mathrm{Fe}\right]$

The magnetic moment of 

$\sqrt{15}$

In ${\mathrm{Fe}}^{+3}$, there are 23 electrons in total.

In light of this, its electronic configuration is-

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^5$

The magnetic moment is therefore $\sqrt{5}(5+1)$ and it has 5 unpaired electrons.

$\begin{array}{r}=\sqrt{30}\\ =5.47\end{array}$

In ${\mathrm{Cr}}^{+3}$, there are 21 electrons in total.

In light of this, its electronic configuration is-

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^3$

The magnetic moment is therefore$\sqrt{3}(3+1)$ and it has three unpaired electrons.

$\begin{array}{r}=\sqrt{1}2\\ =3.46\end{array}$

Thus, the order of magnetic moment is 

$F{e}^{+3}>C{r}^{+3}=M{n}^{+4}$.