Investigation of Dynamic Magnetoelectric Effect in La-doped Z-type Hexaferrites

With the rapid advancement of information technology, there is an increasing demand for compact, energy-efficient electronic devices. Multiferroic materials, which exhibit both ferroelectric and ferromagnetic properties, are promising candidates for next-generation low-power memory and sensing applications. Among them, Z-type hexaferrites, such as Sr₃Co₂Fe₂₄O₄₁ (SCFO), demonstrate intrinsic magnetoelectric (ME) coupling at room temperature, enabling mutual control of magnetization and polarization via external fields. This study focuses on La-doped SCFO ceramics (Sr_3−xLa_xCo₂Fe₂₄O₄₁, x = 0.01-0.04) to investigate the effects of rare-earth substitution on static and dynamic ME coupling. The ceramics were synthesized via solid-state sintering, and their structural, magnetic, and dielectric properties were systematically characterized. Magnetodielectric measurements revealed that all compositions retained ME coupling up to 400 K, with the transverse conical magnetic structure inducing polarization below 2 kOe. Static ME tests showed that La doping slightly reduced polarization strength, while dynamic ME coefficients (α and β) measured by lock-in amplification exhibited strong responses near magnetic phase transitions. Notably, the x = 0.02 composition displayed superior thermal stability, maintaining ME coupling up to 420 K. The results demonstrate that La doping modifies the ME properties of SCFO, offering insights into optimizing room-temperature multiferroic materials for practical applications. This work also highlights the advantages of dynamic ME measurements in probing magnetic phase transitions with high sensitivity.