Interphase exchange coupling and strain-mediated tuning of magnetic and optical properties in BFO-LNFO nanocomposites

Abstract Developing two-phase nanocomposites with tunable magnetoelectric and optical responses is critical for advanced electromagnetic applications. This study reports the synthesis and comprehensive characterization of a novel series of (1 − x )BaFe 12 O 19 (BFO)–La 0.5 Nd 0.5 FeO 3 (LNFO) nanocomposites ( x = 0.00–1.00) via the sol–gel auto-combustion method. Structural analysis using x-ray diffraction and Rietveld refinement confirmed the coexistence of the hexagonal P6 3 /mmc (BFO) and orthorhombic Pbnm (LNFO) phases, with varying crystallite sizes dependent on the LNFO concentration. The optical band gap systematically increases with composition, reaching a maximum of 3.81 eV, indicating tunable electronic structure behavior, accompanied by a blue shift in photoluminescence, attributed to structural distortions and modified electronic band structures. Magnetic measurements demonstrated a competitive interplay between saturation magnetization (Ms) and coercivity (Hc). Notably, the composite with x = 0.75 exhibited a peak coercivity of 10.56 KOe, significantly higher than pure phases, driven by strong interphase exchange coupling. Mössbauer spectroscopy further elucidated the local electronic environment, revealing distinct hyperfine magnetic fields and site occupancy preferences for Fe 3+ ions. Furthermore, microwave analysis indicated that while pure BFO exhibited the highest reflection loss (−34.20 dB), the composites offered tunable absorption bandwidths in the X -band frequency range. These findings establish the BFO-LNFO system as a promising candidate for high-density magnetic recording and high-frequency microwave devices, where property tailoring via phase composition is essential.