In correlated transition-metal oxides, orbital-ordering appears to always precede magnetic ordering ($T_N<T_{\mathrm{OO}}$). The $R{\mathrm{VO}}_3$ series is the exception: it exhibits an inversion of $T_N$ and $T_{\mathrm{OO}}$ with increasing rare-earth radius $R_I$. Why vanadates are different is not understood. Here we show that the reason is fundamental: when lattice effects dominate orbital physics, magnetic order follows orbital order, and thus $T_N<T_{\mathrm{OO}}$. This is what happens in most transition-metal oxides, and it is what quenches exotic quantum orbital phases. In the $R{\mathrm{VO}}_3$ series, however, lattice effects become ineffective with increasing $R_I$, while, at the same time, for antiferromagnetic spin order, the orbital-independent dipolar spin-spin interaction dominates. This has consequences well beyond the $R{\mathrm{VO}}_3$ series itself. In fact, the subtle balance of interactions leading to the $T_N\text{−}{T}_{\mathrm{OO}}$ inversion not only explains why it is so rare, but also gives the criteria for finding it in other materials. The mechanism behind transitions inversion makes such systems an ideal playground for studying unconventional orbital phases. The results presented here rely on the decomposition of the order parameter into irreducible tensors, which allows us to identify the mechanism driving the transition.

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• Magnetic order
• Orbital order
• Strongly correlated systems
• Vanadates
• Dynamical mean field theory