Dielectric, magnetic, and magnetodielectric change mechanisms in Y-type BaSrZn₂Fe₁₂O₂₂ ceramics regulated by doping Al³⁺ and Ga³⁺ ions

We systematically investigated the dielectric, magnetic, and magnetodielectric (MD) properties of Y-type hexaferrite doped with Al³⁺ and Ga³⁺ ions. Al³⁺ ions preferentially enter the spin-up octahedral lattice sites while Ga³⁺ ions occupy the spin-down octahedral lattice sites first and then, enter the spin- octahedral sites with the increase in doping amount. The initial magnetization reaches saturation from outside of the hysteresis loops, exhibiting a non-collinear spin order. The step-like increase in magnetization with magnetic field indicates the ferroelectric changes in longitudinal conical spin order. The positive MD effect at low temperatures and the negative MD effect after warming for the doped samples are controlled by non-collinear spin ordering and electron hopping, respectively. The Al-doped and Ga-doped samples exhibit different ferroelectric behaviors driven by magnetic fields. Their ferroelectric phase diagrams were proposed on the basis of magnetic and MD properties. The results associate the physical properties with the doped ions in Y-type hexaferrite.