Unusual dielectric properties of hollow magnesium ferrite nanospheres: a potential lightweight microwave absorber

We present a combination of dielectric and magnetic experimental signatures on MgxFe3-xO4 (x = 0.0, 0.2, 0.3, 0.4 and 1.0) nano-hollow spheres (NHSs) magnetic semiconductor system. Interestingly, Mg0.3Fe2.7O4 NHSs with the maximum value of room temperature dielectric permittivity behave as negative index material in the vicinity of metamagnetic transition. Detailed study reveals that high dipolar fluctuation-assisted back-scattering under strong spin-polaron coupling results in negative dielectric index, while metamagnetic transition takes place due to the ferromagnetic arrangement of spins by overcoming the super-exchange interaction in Mg0.3Fe2.7O4 NHSs. Finally, an excellent electromagnetic wave absorbing efficiency with reflection loss (RL)= - 53.8 dB in the 1-20 GHz range is achieved by utilizing high room temperature dielectric and magnetic loss, and the hollow interior of Mg0.3Fe2.7O4 NHSs, opening up a plethora of interesting possibilities in lightweight shielding devices, and waveguides for microwave applications.

Automated summary

This study presents a combination of dielectric and magnetic experimental signatures on MgxFe3-xO4 (x = 0.0, 0.2, 0.3, 0.4, and 1.0) nano-hollow spheres (NHSs) magnetic semiconductor system. Interestingly, Mg0.3Fe2.7O4 NHSs exhibit negative refractive index characteristics when they have the highest room temperature dielectric permittivity. The study further investigates the impact of high dipolar fluctuation-assisted back-scattering and strong spin-polaron coupling on the negative dielectric index, as well as the metamagnetic transition in Mg0.3Fe2.7O4 NHSs. The research demonstrates that by utilizing the high room temperature dielectric and magnetic loss, as well as the hollow interior of Mg0.3Fe2.7O4 NHSs, excellent electromagnetic wave absorption efficiency can be achieved for microwave applications.