Epsilon-Fe2O3 is an iron oxide polymorph that is stable only at the nanoscale. Epsilon-Fe2O3 has a complex magnetic structure that changes from a high temperature ferrimagnetic state to a low temperature noncollinear magnetic ground state. Similar to gamma-Fe2O3, epsilon-Fe2O3 consists of Fe3+ ions in octahedral and tetrahedral coordinations but with two distorted octahedral sites.

In this work we synthesized Co, Ni, and Cu doped epsilon-Fe2O3 nanoparticles using a reverse micelle sol-gel method. The changes caused by doping epsilon-Fe2O3 nanoparticles provided insights into the complex magnetic ground states and as well as the unusual distortion in the octahedral sites. Furthermore, doping allowed us to tune the magnetic properties of epsilon-Fe2O3, opening up further applications for this unique material.