Terahertz Faraday Rotation of SrFe₁₂O₁₉ Hexaferrites Enhanced by Nb Doping

Abstract

The magneto-optical and dielectric behavior of M-type hexaferrites as permanent magnets in the THz band is essential for potential applications like microwave absorbers and antennas, while are rarely reported in recent years. In this work, single-phase SrFe12–x Nb x O19 hexaferrite ceramics were prepared by the conventional solid-state sintering method. Temperature dependence of dielectric parameters was investigated here to determine the relationship between dielectric response and magnetic phase transition. The saturated magnetization increases by nearly 12%, while the coercive field decreases by 30% in the x = 0.03 composition compared to that of the x = 0.00 sample. Besides, the Nb substitution improves the magneto-optical behavior in the THz band by comparing the Faraday rotation parameter from 0.75 (x = 0.00) to 1.30 (x = 0.03). The changes in the magnetic properties are explained by a composition-driven increase of the net magnetic moment and enhanced ferromagnetic exchange coupling. The substitution of the donor dopant Nb on the Fe site is a feasible way to obtain multifunctional M-type hexaferrites as preferred candidates for permanent magnets, sensors, and other electronic devices.

Exploring the role of oxygen vacancies on the magnetic and electromagnetic absorption properties of La3+-modified M-type hexaferrite with Al3+ doping

“…This improvement was achieved by lowering the natural resonance frequency ( f r ) and enhancing impedance matching. The substitution of the rare-earth element in place of divalent M 2+ in the M-type hexaferrite will enhance the reduction of Fe 3+ to Fe 2+ cation with the formation of oxygen vacancies [20,28]. The substitution of La 3+ in the M-type hexaferrite also reported that the conversion of Fe 3+ to Fe 2+ is enhanced with the generation of oxygen vacancies and affects the electronic and magnetic properties [29,30].…”

“…Zhu et al [19] reported that the electrical conduction and relaxation behaviours of BaFe 10.2 Sc 1.8 O 19 M-type hexaferrite is contributed mainly by the movable oxygen vacancies. The electronic and magnetic characteristics of M-type hexaferrite were also reported to be affected by introducing oxygen vacancies or defects [20,21]. These oxygen vacancies or defects can be created through synthesis conditions (temperature and pressure) or cationic substitution methods.…”