Prediction of large magnetoelectric coupling in Fe4N/BaTiO3 and MnFe3N/BaTiO3 junctions from a first-principles study

Abstract

The magnetoelectric (ME) effects of Fe₄N/BaTiO₃ and MnFe₃N/BaTiO₃ junctions are investigated using first-principles calculations. Compared with the very weak ME coupling effects for FeN/TiO₂ interfaces in both Fe₄N/BaTiO₃ and MnFe₃N/BaTiO₃ junctions, the large ME coefficients are achieved at the more stable Fe₂/TiO₂ interface in the Fe₄N/BaTiO₃ junction and the more stable MnFe/TiO₂ and Mn₂/TiO₂ interfaces in the MnFe₃N/BaTiO₃ junction. The magnetoelectric effect originates from the interface bonding mechanism which alters the chemical bonding and the hybridization at the interface when the electric polarization reverses. In addition, from the detailed analysis, we find that the interfacial Fe^II(Mn^II) (the face-centered sites Fe or Mn in Fe₄N and MnFe₃N) atom plays a more important role in the ME coupling than the interfacial Fe^I(Mn^I) (the corner sites Fe or Mn in Fe₄N and MnFe₃N) atom. These results suggest that Fe₄N/BaTiO₃ and MnFe₃N/BaTiO₃ junctions could be designed as multiferroic materials with large magnetoelectric coupling under their more stable interfaces. And the magnetic Mn-substitution doping at the interfacial Fe^II position in the Fe₄N/BaTiO₃ junction can possibly obtain a relatively large ME coefficient difference compared with doping at the interfacial Fe^I position.