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Perovskites oxides, which have the general formula ABO3, are widely studied by theoretical or experimental means due to the large variety of intriguing properties, such as ferroelectricity, piezoelectricity, multiferroicity and others.1-3 One fascinating feature for this structure is the capability to control the existence of different properties from chemical substitution and doping at Aand B-sites.4 For example, the ilmenite structure based on very common mineral of earth surface (FeTiO3), allows a high compositional diversity of A2+ and B4+ cations that occupy alternate basal-planes along the [001] hexagonal axis of a ordered corundum structure.5 The most studied ilmenite materials are Ti-based compounds with different A2+ (A = Mn, Fe, Ni, Co) cations, although other materials are found in this symmetry.6-9 In relation to the magnetic ordering of ilmenite materials, mainly ATiO3 (A = Mn, Fe, Ni, Co), Goodenough and Stickler proved that such materials are antiferromagnetic insulators and have two different magnetic couplings constants: Intralayer (J1) and Interlayers (J2), as shown in Figure 1. For J1, the magnetic exchange happens between A-O-A atoms and is dominated by the coupling of a t2g orbital in one cation with an eg orbital in other. Thus, the signal for exchange parameter depends upon the occupancies of the interacting orbitals making MnTiO3 antiferromagnetic and FeTiO3, CoTiO3, NiTiO3 ferromagnetic for intralayer coupling (J1). The J2 interactions are mediated by the BO6 clusters in the intermetallic connection A-O-B-O-A with a less contribution of a direct overlap in [001] direction due to the vacancy in cationic sublattice (Figure 1) with opposite magnetization directions between adjacent A layers (antiferromagnetic).5,10 In Fe-based ilmenite materials, aim of this study, the antiferromagnetic ordering is stabilized by the long-range exchange coupling (J2). Therefore, J2 is the responsible for magnetic ordering control of these materials. As previously discussed, J2 depends of intermetallic connection Fe-O-BO-Fe suggesting that the non-magnetic B-site replacement can control the magnetism for such materials. Other kind of materials show superexchange interactions (A-O-B-O-A) as the key for magnetic ordering control, for instance, A2BO6 and AA’3B4O12 compounds.11 Shiraki and co-workers reported that A-site ordered perovskites CaCu3Ge4O12 and CaCu3Sn4O12, which are isostructural to antiferromagnetic CaCu3Ti4O12, are ferromagnets.12 Mizumaki and co-authors using X-ray absorption spectroscopy (XAS) for such materials proved that the antiferromagnetism in CaCu3Ti4O12 can be explained by strong hybridization of the Cu 3d, Ti 3d and O 2p orbitals, while CaCu3Ge4O12 and CaCu3Sn4O12 spectra shows hybridization only for Cu 3d and O 2p orbitals.13 Similar results are found in ab initio predictions performed by Toyoda and co-workers to investigate the magnetic coupling constants of CaCu3B4O12 (B = Ti, Ge, Zr and Sn) from energetic and Density of States calculations.14 Such simulations clarify the magnetic Artigo Geral 47

Interplay Between Interatomic Distance and Orbital Overlap at Control of Magnetism in FeBO3 (B = Ti, Ge, Zr, Sn) Ilmenites