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Article Dans Une Revue Inorganic Chemistry Année : 2012

Case of a strong antiferromagnetic exchange coupling induced by spin polarization of a Mn-Mn partial single bond.

Hélène Bolvin
Frank Richard Wagner
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Résumé

The large antiferromagnetic coupling in the Mn(IV)-Mn(IV) bond in the Li(6)Ca(2)[Mn(2)N(6)] and Li(6)Sr(2)[Mn(2)N(6)] crystals (J = -739 and -478 cm(-1), respectively, with H = -JS(A)*S(B)) is studied using different theoretical methods: solid-state density functional theory calculations, molecular density functional theory, and post-Hartree-Fock calculations with large embeddings. This magnetic coupling is a challenge for theoretical methods because both correlation and polarization effects are crucial for the correct description of the bond. All methods predict a large antiferromagnetic coupling, but none of the considered methods give a quantitative agreement with the experimental values. The molecular methods, except B3LYP and CASPT2, underestimate the coupling for the calcium compound, while they overestimate it in the strontium compound, within 30%. These methods, on the other hand, strongly underestimate the decrease of the coupling between the two compounds, with the most correlated one predicting the same value for both compounds. The solid-state method overestimates the coupling within 60% but reproduces better their ratio. Analysis of the calculations shows that the magnetic coupling between the local π orbitals is not caused by a direct interaction but by the spin-polarized σ bond.
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Dates et versions

hal-00763713 , version 1 (11-12-2012)

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Hélène Bolvin, Frank Richard Wagner. Case of a strong antiferromagnetic exchange coupling induced by spin polarization of a Mn-Mn partial single bond.. Inorganic Chemistry, 2012, 51 (13), pp.7112-8. ⟨10.1021/ic2027237⟩. ⟨hal-00763713⟩
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