Zn-doped cobalt ferrite: Tuning the interactions by chemical composition

Magnetic nanoparticles represent complex but very interesting objects. They combine the bulk properties with novel phenomena emerging at the nanoscale due to finite-size effects. The recent development of the synthetic procedures allows having a strong control on the size and shape of individual particles and on their physical-chemical structure. Among different magnetic materials, spinel ferrite nanoparticles offer strong chemical and physical stability as well as tunable magnetic properties. In the present article, we investigate the effect of Zn substitution in cobalt ferrite nanoparticles. The technological development of nanoparticle-based magnetic materials aims to find a balance between a well-defined magnetic behavior of individual elements and their strong interactions, which arise from the need of miniaturization that leads to dense ensembles of the system's constituents. Within this complex context, we provide one route to optimize the properties of small spinel ferrite particles by tuning their chemical composition without compromise their structural properties, and with full control of their size and shape. Furthermore, we propose an advanced analysis of their magnetic properties in the framework of the random anisotropy model. We will show that the chemical composition not only determines the intrinsic anisotropy energy of each nanoparticle but also owns a profound effect on the interparticle interactions.