High-entropy spinel ferrites MFe₂O₄ (M = Mg, Mn, Fe, Co, Ni, Cu, Zn) with tunable electromagnetic properties and strong microwave absorption

Ferrites are the most widely used microwave absorbing materials to deal with the threat of electromagnetic (EM) pollution. However, the lack of sufficient dielectric loss capacity is the main challenge that limits their applications. To cope with this challenge, three high-entropy (HE) spinel-type ferrite ceramics including (Mg_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2)Fe₂O₄, (Mg_0.2Fe_0.2Co_0.2Ni_0.2Cu_0.2)Fe₂O₄, and (Mg_0.2Fe_0.2Co_0.2Ni_0.2Zn_0.2)Fe₂O₄ were designed and successfully prepared through solid state synthesis. The results show that all three HE MFe₂O₄ samples exhibit synergetic dielectric loss and magnetic loss. The good magnetic loss ability is due to the presence of magnetic components; while the enhanced dielectric properties are attributed to nano-domain, hopping mechanism of resonance effect and HE effect. Among three HE spinels, (Mg_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2)Fe₂O₄ shows the best EM wave absorption performance, e.g., its minimum reflection loss (RL_min) reaches −35.10 dB at 6.78 GHz with a thickness of 3.5 mm, and the optimized effective absorption bandwidth (EAB) is 7.48 GHz from 8.48 to 15.96 GHz at the thickness of 2.4 mm. Due to the easy preparation and strong EM dissipation ability, HE MFe₂O₄ are promising as a new type of EM absorption materials.