Magnetic moment 3.89 B.M. is given by (Atomic numbers Ni = 28, Ti = 22, Cr = 24, Co = 27)

$\begin{array}{l}T{i}^{3+}\Rightarrow d^{1}1unpairede\therefore \mu =1.73BM\\ C{r}^{2+}\Rightarrow d^{4}4unpaired{e}^{\text{'}}s\therefore \mu =4.98BM\\ C{o}^{2+}\Rightarrow d^{7}3unpaired{e}^{\text{'}}s\therefore \mu =3.89BM\\ N{i}^{2+}\Rightarrow d^{8}2unpaired{e}^{\text{'}}s\therefore \mu =2.83{\rm B}{\rm M}\end{array}$