Influence of the cation distribution, atomic substitution, and atomic vacancies on the physical properties of $CoFe_2O_4$ and $NiFe_2O_4$ spinel ferrites

Kedar Sharma (1) , Lionel Calmels (1) , Dongzhe Li (1) , Antoine Barbier (2, 3) , Rémi Arras (1)

1 CEMES-MEM - Matériaux et dispositifs pour l'Electronique et le Magnétisme
2 SPEC - UMR3680 - Service de physique de l'état condensé
3 LNO - Laboratoire Nano-Magnétisme et Oxydes

$CoFe_2O_4$ and $NiFe_2O_4$ are well-known insulating and ferrimagnetic spinel ferrites with high Curie temperatures, an important characteristic for electronic and spintronic applications. We used first-principles calculations to investigate how their electronic and magnetic properties can be altered or tuned by the presence of structural point defects. We considered successively the effects of cation distribution in the spinel lattice for stoichiometric compounds and of atom substitutions or vacancies. Our calculations demonstrate that a deviation from the perfectly inverse distribution of cations increases the magnetization and decreases the width of the band gap at the Fermi level. In contrast to cation vacancies, oxygen vacancies are not expected to strongly affect the magnetization. We show that $NiFe_2O_4$ crystals with an excess of Ni cations can display a spin-polarized hole conductivity. We finally calculated the formation energy of the different defects and we give details on their gap states.

Domains: Condensed Matter [cond-mat]

Kedar Sharma, Lionel Calmels, Dongzhe Li, Antoine Barbier, Rémi Arras. Influence of the cation distribution, atomic substitution, and atomic vacancies on the physical properties of $CoFe_2O_4$ and $NiFe_2O_4$ spinel ferrites. Physical Review Materials, 2022, 6 (12), pp.124402. ⟨10.1103/PhysRevMaterials.6.124402⟩. ⟨hal-03937409⟩