Electronic Structure And Magnetism Of P-n Codoped In₂O₃-based Diluted Magnetic Oxides

Recently,dilute magnetic semiconductors?DMSs?have provoked considerable interest for application in spin-based devices,which combine the spin and charge fundamental degrees of freedom within a single material.Indium oxide?In₂O₃?,an optically transparent,high electrical conductivity,wide-band-gap?3.75 eV?semiconductor with a cubic bixbyite structure has been considered as a promising candidate as a host matrix for room-temperature ferromagnetic ordering.Although here have been many reports on the observation of room-temperature ferromagnetic ordering in TM-doped In₂O₃ prepared by different synthesis methods,the mechanism for the origin of ferromagnetism is still controversial.In this paper,the electronic structures and magnetic properties of p-n codoped In₂O₃ diluted magnetic oxides were investigated by the first-principles calculation based on density functional theory,and the origin of ferromagnetic ordering was discussed.1.The electronic structures and magnetic properties of the Co/Sn codoped In₂O₃ systems are systematically investigated by the first-principles calculation based MedeA-VASP software,and the stability of the doped Co atoms located in substitutional sites and interstitial sites is also discussed by the thermodynamic and kinetic characteristics in the In₂O₃ lattice.It was found that for the Co-doped In₂O₃,the substitutional Co atoms are more stable in the In₂O₃ lattice.With introducing Sn atoms,the formation energy of substitutional Co atoms is lower,implying a higher solid solution of Co atoms in the In₂O₃ lattice.It may be due to that the Coulomb electrostatic attraction from the codoping of Co and Sn atoms forms p-n pairs of electronics and holes with opposite charge states,which can activate the substitution of Co atoms in the In₂O₃ lattice.For the Co-doped In₂O₃,the Co-O-Co superexchange interactions will be antiferromagnetism in nature.So the long-range ferromagnetic interactions could not be activated.However,the Sn codoping leads a stable ferromagnetic ground state with?E_FM-AFM?-260 meV,and also change the magnetic interaction between neighboring Co atoms from antiferromagnetic to ferromagnetic due to the hybridization interaction among Co3d,O 2p and Sn 5s orbitals.Further calculations show that even introducing the neutral oxygen vacancies?V_O⁰?defects,the systems still show antiferromagnetic ground states and do not change the antiferromagnetic magnetic interaction between neighboring Co atoms.2.The electronic structures and magnetic properties of the Cu/Sn codoped In₂O₃systems are systematically investigated by the first-principles calculation.It was found that for the Cu-doped In₂O₃,the substitutional Cu atoms are in a more stable structure in the In₂O₃lattice,That is the same as the O-rich growth conditions from the thermodynamic characteristic.With introducing Sn atoms,the formation energy of substitutional Cu atoms is lower.For the Cu-doped In₂O₃,the systems do not show ferromagnetic ground states.However,the Sn codoping leads a weak ferromagnetic ground state with?E_FM-AFM=-24.3meV,still due to the hybridization interaction among Co 3d,O 2p and Sn 5s orbitals.In order to obtain a more stable ferromagnetic ground state,we use an N atom substitutes the O atom between two Cu atoms in the In₂O₃ lattice.For Cu/N and Cu/N/Sn codoped In₂O₃,the formation energy of substitutional Cu atoms is lower than interstitial Cu atoms in O-rich growth conditions,and leads stable ferromagnetic ground state with?E_FM-AFM=-131.3 and-142.9 meV,respectively.The stable ferromagnetic ground states may be due to the p-d hybridization of Cu-N and Cu-O,and the p-p coupling between N 2p and O 2p states.