Study On The Magnetoelectric Properties Of Ilmenite-type ABO₃

Ilmenite-type ABO₃ compounds have been extensively studied by researchers around the world due to their excellent physical and chemical properties.The physical properties of this kind of compounds are affected by the selection of the B-site ions.The crystal-field effect and strongly correlation interaction of 3d compounds,such as Zn MnO₃ and Mg MnO₃,are dominant,and then we don't need to take spin-orbit coupling(SOC)into account in our first-principle study.On the other hand,the 5d compound Mg IrO₃ is complex,due to the intenstive SOC,so it is more complicated to study than the 3d compound.In this article,we perform first-principles calculations on two types of compounds to explore their respective properties.First of all,for the difference in the magnetic ground states of the 3d compounds ZnMnO₃ and MgMnO₃,we believe that it is mainly caused by the competition between the two exchange paths in J₁.The two paths are the direct exchange interaction which exhibits antiferromagnetism and the superexchange interaction which exhibits ferromagnetism,respectively.In Mg MnO₃,it prefers to direct exchange interaction,giving rsie to the antiferromagnetic J,while strong hybridization betweem the 3d¹⁰obital of Zn and the 2p orbital of O ions leads to the ferromagnetic superexchagne interaction dominantly,forming the zigzag antiferromagnetic magnetic ground state.Our results indicate that the existence of non-magnetic cation Zn is the fundamental origin of the different magnetic ground states of the two isomorphic compounds.Secondly,for the 5d compound MgIrO₃,the SOC provides more possibilities for the novel properties of ilmenite-type compounds.We explored the evolution of the electronic structure as a function of the spin orientation.Our result revealed that in the(1,0,0)orientation,the compound exhibits the insulating feature,and the band gap increases when the Hubbard U increases.When it deviates from(1,0,0),the band gap is reduced.In addition,the components of the orbital magnetic moment rotate with the change of the orientation,however,the net magnetic moment remains constant.Finally,according to the static energies,we found that the(1,0,0)orientation possesses the lowest one,suggesting that it is the easy magnetic axis.From 100directon to 010 one,the static energies modifies regularly with a period of 60°,is consistent with the two-dimensional honeycomb symmetry of ilmenite-type structure.