Innovative materials, particularly multiferroics, have the potential to transform technology. Full optimization of their usage will require an in-depth understanding of the underlying electronic and magnetic interactions. One such material is $\epsilon \text{−}{\mathrm{Fe}}_2{\mathrm{O}}_3$. However, because this hard ferrimagnet with strong magnetoelectric coupling is composed of only ${\mathrm{Fe}}^{3+}$, distinguishing the role of the various sites is incredibly challenging. To overcome this challenge, ${\mathrm{Cr}}^{3+}$ ions were doped into the ${\mathrm{DO}}_{h1}$ sites of $\epsilon \text{−}{\mathrm{Fe}}_2{\mathrm{O}}_3$ nanoparticles, effectively creating electron deficient defects. The $\epsilon$-(${\mathrm{Fe}}_{1-x}{\mathrm{Cr}}_x{)}_2{\mathrm{O}}_3$ ($x=0.01$ to 0.12) nanoparticles have reduced ${\mu }_0{H}_C\left(T\right)$ and $M_S\left(T\right)$ as the Cr concentration increases. The impact of Cr doping on the local electronic and magnetic structure is characterized. At 10 K, subtle changes are measured, with the ${\mathrm{T}}_d$ site electrons becoming increasingly localized as the concentration of electron-deficient ${\mathrm{DO}}_{h1}$ sites increases. Far more dramatic changes occur at 300 K, when the ${\mathrm{T}}_d$ site of the $\epsilon$-(${\mathrm{Fe}}_{1-x}{\mathrm{Cr}}_x{)}_2{\mathrm{O}}_3$ splits into two distinct local environments with ${\mathrm{Fe}}^{2+}$ and ${\mathrm{Fe}}^{4+}$ character. The nature of this splitting suggests that dynamic electron interactions play a significant role in $\epsilon \text{−}{\mathrm{Fe}}_2{\mathrm{O}}_3$'s magnetic anisotropy and magnetoelectric properties.

• Received 2 December 2023
• Accepted 23 January 2024

DOI:https://doi.org/10.1103/PhysRevMaterials.8.024407