The orbital and spin ordering configurations of two perovskite compounds $LaV{O}_3$ and $LaMn{O}_3$

are shown below $($one unit cell in each case$).$ Only the relevant transition metal orbitals $(V^{3+}$ or

$M{n}^{3+})$ are shown. $L{a}^{3+}$ is non$-$magnetic and is not shown as it does not take part in determining

the orbital or spin ordering; oxygen anions $(O^{2-})$ link the transition metals and their positions are

represented by black dots. Explain, in terms of superexchange interactions, why $LaV{O}_3$ and

$LaMn{O}_3$ have different magnetic ordering configurations.

a $,LaV{O}_3$

b $LaMn{O}_3$