Evaluation of Neel Temperatures from Fully Self-Consistent Broken-Symmetry GW and High-Temperature Expansion: Application to Cubic Transition-Metal Oxides

Using fully self-consistent thermalbroken-symmetry GW, we constructeffective magnetic Heisenberg Hamiltonians for a series of transitionmetal oxides (NiO, CoO, FeO, and MnO), capturing a rigorous but condenseddescription of the magnetic states. Then applying high-temperatureexpansion, we find the decomposition coefficients for spin susceptibilityand specific heat. The radius of convergence of the found series determinesthe Neel temperature. The NiO, CoO, and FeO contain a small ferromagneticinteraction between the nearest neighbors (NNs) and the dominant antiferromagneticinteraction between the next-nearest neighbors (NNNs). For them, thederived Neel temperatures are in good agreement with experiment.The case of MnO is different because both NN and NNN couplings areantiferromagnetic and comparable in magnitude, for which the errorin the estimated Neel temperature is larger, which is a signatureof additional effects not captured by electronic structure calculations.

Automated summary

Using fully self-consistent thermal-broken symmetry GW, effective magnetic Heisenberg Hamiltonians are constructed for a series of transition metal oxides (NiO, CoO, FeO, and MnO), accurately describing their magnetic states. By applying high-temperature expansion, the decomposition coefficients for spin susceptibility and specific heat are obtained. The Néel temperatures are determined by the radius of convergence of the series, and the agreement between the derived Néel temperatures and experimental results is good for NiO, CoO, and FeO, but less accurate for MnO, which may suggest additional effects not accounted for by electronic structure calculations.