Static and dynamic magnetic study of DyFexAl12−x (4 ≤ x ≤ 4.7)

Mössbauer spectroscopy, magnetization and AC-susceptibility measurements performed on DyFexAl12−x (4 ≤ x ≤ 4.7) polycrystalline samples (ThMn12-type structure), revealed a complex magnetic behaviour dependent on applied field, temperature and composition. The transition temperature below which magnetic interactions are observed for a significant fraction of Fe atoms in Mössbauer spectra decreases from 180 K for x = 4 down to 155 K for 4.2 ≤ x ≤ 4.5 and rises again up to 185 K for x = 4.7. Comparing with the isostructural Y and U containing analogs the present study reveals that Dy has little influence on the Fe sublattice magnetic properties, which are rather driven by the antiferro 8f–8f interactions and ferro 8f–8j interactions. AC-susceptibility evidences for all compositions, including the ordered DyFe4Al8, iron-rich nanoclusters with short-range ferromagnetic-like order above room temperature.