Dynamic magnetic and dielectric behavior of single crystal lead substituted barium hexaferrite

M-type barium hexaferrites from the (Ba, Pb)Fe12O 19 family show a dramatic influence of lead-doping on dielectric, magnetic, as well as optical properties. The parent compound BaFe 12 O 19 is a well-known semiconducting ferrimagnet with broad range of application. On the other hand, the PbFe 12 O 19 material shows both ferromagnetic and ferroelectric properties above the room temperature. Spin and charge of iron ions within the structure of this system suggest there might a coupling between magnetic and dielectric excitations. We report on our investigation of dynamic magnetic and dielectric properties on single- crystalline lead-substituted hexaferrite (Ba, Pb)Fe 12 O 19 . On the basis of ac magnetic susceptibility and dielectric spectroscopy in radio-frequency range and low temperatures we show that the presence of lead in (Ba, Pb)Fe 12 O 19 , as compared to pristine BaFe 12 O 19 , leads to emergence of pronounced relaxations both in dielectric and magnetic sector. Their characteristic relaxation times and activation energies are similar which suggests a bi- relaxor nature of the chosen composition of (Ba, Pb)Fe 12 O 19 . We discuss the dispersion of these relaxations and their origin in the context of magnetic domains walls and the influence of doping on the crystal lattice dynamics of the M-type barium hexaferrite. This work was supported by the Russian Ministry of Education and Science Project 5-100 and Croatian Science Foundation projects IP-2013-11-1011 and IP-2018-01-2730. References: rd [1] L. Alyabyeva et al., Proceedings of the 43 International Conference on Infrared Millimeter and Terahertz Waves (IRMMW-THZ) (2018) [2] S. E. Rowley et al., Scientific Reports 6, 25724 (2016). [3] S. E. Rowley et al., Phys. Rev. B 96, 020407(R) (2017). [4] E. S. Zhukova et al., Solid State Sciences 62, 13 (2016). [5] G. L. Tan and W. Li, J. Am. Ceram. Soc. 98, 1812 (2015).