Antiferromagnetic–Ferromagnetic Transition in Cubic EuTiO_3−δF_δ Thin Films via Fluorine Substitution

Here, we report a method that combines postannealing and fluorination in a reducing atmosphere to achieve an electron redistribution in a EuTiO_3-δF_δ (FETO) film grown on SrTiO₃ (STO) substrates. Differing from the traditional fluorine doping with a strain effect, the fluorinated films treated at a higher temperature remain an unstrained cubic structure. Such fluorine substitution facilitates substantial modification of the bonding and electronic structure within the films, thereby inducing a transition from antiferromagnetic to ferromagnetic behavior. This work provides a specific perspective on the role of anion doping in magnetic transitions through fluorine doping, particularly under the condition that the strain effect is effectively eliminated.