We report on the magnetic behavior of oxidized-CoxFe1-xS2 nanocrystals as they assemble to form nanoparticles. The morphologies show a typical NP size of around 250–100 nm and NC sizes of around 7 nm. Using extended absorption fine structure, we confirm the existence of Co-oxides for x≥ 0.5. The temperature dependence of DC magnetization and AC susceptibility reveals a number of magnetic phases in these NP oxides. Co-existence of blocking and freezing behaviors via intercluster dipolar interactions is found consistent with the antiferromagnetic exchange interactions within clusters embedded within a “supermagnetic” ensemble. The Fe substitution influences the supermagnetism of the ensemble, while the AF behavior of the embedded clusters remains largely unaffected. The overall behavior can be described by a phase diagram which can be understood in terms of competition between the various dipolar, inter-, and intracluster interactions within the random magnetic anisotropy model. Graphical abstract: [Figure not available: see fulltext.].
|Journal||Journal of Materials Research|
|State||Published - 9 Jan 2023|