Spinel-hexagonal nanocomposites have attracted a lot of interest for high-performance microwave absorbers due to their ability to simultaneously modify the dielectric and magnetic loss processes. The soft ferrite Ni0.55Cu0.2Zn0.25Fe2O4 (NCZFO) and the hard M-type hexaferrite BaFe12O19 (BFO) were effectively synthesized using a sol–gel auto-combustion process. Physical mixing was used to create a composite of (1–x) NCZFO + (x) BFO (x = 0.00, 0.25, 0.50, 0.75, and 1.00). The structural analysis confirms the coexistence of cubic spinel and hexagonal magnetoplumbite phases. Magnetic measurement reveals a change from soft to hard magnetic behavior as the hexaferrite fraction rises, as well as enhanced coercivity and changed phase exchange interactions. Electron spin resonance investigations provide additional evidence for strong interfacial magnetic coupling and anisotropy evolution in the composite system. In the X-band frequency range (8–12 GHz), the composite structures show a significant improvement in microwave absorption performance when compared to the individual phases. The ideal composition x = 0.75 exhibits a reflection loss of roughly − 42 dB at 10.4 GHz with an absorber thickness of 3 mm, which corresponds to more than 90

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)BaFe12O19 (BFO)-La0.5Nd0.5FeO3 (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 P63/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. M & ouml;ssbauer spectroscopy further elucidated the local electronic environment, revealing distinct hyperfine magnetic fields and site occupancy preferences for Fe3+ 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.

The controlled substitution of Ag into Mn-Zn spinel ferrites offer a promising strategy to tailor their magnetic and dielectric properties for advanced functional devices. In this study, Mn0.5Zn0.5Ag3xFe2-xO4 (x <= 0.08) nanospinel ferrites were synthesized via a sol-gel route to investigate the influence of Ag on structure, cation distribution, magnetic behavior, and charge transport. X-ray diffraction confirmed a cubic spinel phase with crystallite sizes ranging from 18.1 nm (x = 0.02) to 26.4 nm (x = 0.00), accompanied by lattice expansion due to Ag + incorporation at octahedral sites. Mo & uml;ssbauer spectroscopy revealed Fe3+ site redistribution and the presence of a minor alpha-Fe2O3 phase starting from x = 0.02. Magnetic measurements showed a non-monotonic variation in saturation magnetization, peaking at 209.29 emu/g (RT) for x = 0.02, linked to optimized Fe3+-O2--Fe3+ superexchange and secondary phase effects, while all samples exhibited soft magnetic nature at 10 K. AC conductivity followed Jonscher's law, with the lowest activation energy (Ea) (0.39 eV) for the undoped ferrite and maximum conductivity at x = 0.06 due to enhanced Fe2+/Fe3+ hopping. Dielectric analysis indicated Maxwell-Wagner interfacial polarization with composition-dependent trends, and impedance spectroscopy confirmed dual grain and grain-boundary relaxation. These findings establish Ag substitution as an effective means to engineer the coupled magnetic-dielectric response of Mn-Zn ferrites, enabling application-specific tuning in soft magnetic and spintronic systems.

Nanoparticles of Dy–Ce co-substituted M-type strontium hexaferrite with the general formula SrDyxCexFe12-2xO19 (x = 0.00–0.10) were synthesized by sol–gel auto-combustion method. X-ray diffraction (XRD) confirmed the formation of the hexagonal magnetoplumbite phase (space group P63/mmc) with a minor α-Fe2O3 impurity at intermediate substitution levels. Raman spectroscopy confirmed the formation of the magnetoplumbite hexagonal structure and indicated structural modifications induced by Dy–Ce co-substitution, and X-ray photoelectron spectroscopy (XPS) confirmed the presence of Fe3+/Fe2+, Ce3+/Ce4+, Dy3+ and lattice oxygen with oxygen vacancies, FE-SEM and HR-TEM studies identified the hexagonal plate-like nanostructures with improved grain homogeneity for x = 0.04, while EDS confirmed the successful doping of Dy and Ce without any impurity elements. The BET analysis showed a maximum specific surface area of 15.06 m2 g −1 for the x = 0.04 composition, which showed the enhancement of mesoporosity as a result of rare-earth substitution. Electrochemical measurements indicated that the maximum specific capacitance of the x = 0.04 sample was 983.8 F g−1 from cyclic voltammetry at 10 mV s−1 and 510.6 F g−1 from galvanostatic charge–discharge at 1 mA g−1 with 87% capacitance retention after 5000 charge–discharge cycles. Electrochemical impedance spectroscopy revealed reduced charge-transfer resistance and accelerated ion transport upon rare-earth substitution. The best photocatalytic performance was observed for the composition of x = 0.10 with 91.6% degradation of malachite green dye under solar irradiation and a first order rate constant of 0.01104 min−1. The results reveal that the Dy–Ce co-substitution is advantageous to the structural, electrochemical, and photocatalytic properties of the M-type strontium hexaferrite.

Ni-Zn-Mg ferrite nanoparticles were synthesized via the sol-gel method for magnetic hyperthermia. XRD and FT-IR confirm a cubic spinel structure, while SEM/EDS verify morphology and elemental composition. The nanoparticles exhibit high saturation magnetization and achieve a SAR (Specific Absorption Rate) of similar to 50.34 W/g at 5 mg/mL under an alternating magnetic field (approximate to 334 Oe, 276 kHz).

We report an all-inclusive account of the gas sensing behaviour of the nanocrystalline Ni-Cu-Zn ferrites formulated as Zn0.5Ni0.5-xCuxFe2O4 (x = 0-0.5, keeping Delta x = 0.1) synthesized by a sol-gel route. Structural characterization by X-ray diffraction reveals the creation of a single spinel phase within the synthesized crystals. Cu doping up to x = 0.4 caused an enhancement in the lattice parameter. However, increasing the doping concentration to x = 0.5 introduce significant lattice imperfections, leading to a non-linear variation in the parameter. The particle size obtained from XRD data varies between 17 and 26 nm (Scherer method) and 36-64 nm (Williamson-Hall method). Porosity values >= 47% reveal the porous nature of the ferrites. Scanning Electron Microscopy (SEM) analysis shows agglomerated nanocrystals, with sizes between 32 and 38 nm. The Ni-Cu-Zn gas sensor (x = 0.4) demonstrates high sensitivity (73%) and swift response (54 s) as well as recovery (71 s) times for ammonia sensing. The sensor's ability to not only detect ammonia gas but also quantitatively analyze it with moderate response and recovery makes it a suitable option for ammonia gas sensing applications.

ABSTRACT In this work, ZnAl0.1Sn0.1Fe1.8O4 (ZASFO) ferrites were synthesized via a sol–gel auto‐combustion route and sintered at 800°C, 1000°C, and 1200°C to systematically investigate the influence of thermal processing on vibrational, elastic, and dielectric properties. X‐ray diffraction confirms the formation of a single‐phase cubic spinel structure for all samples. FT‐IR analysis reveals characteristic tetrahedral (ν1) and octahedral (ν2) metal–oxygen stretching modes, from which site‐specific force constants were evaluated. The tetrahedral force constant increases markedly with sintering temperature, indicating enhanced lattice rigidity and improved crystallinity. Elastic moduli derived from IR‐based lattice dynamical analysis show increased stiffness, sound velocity, and Debye temperature at higher sintering temperatures, reflecting strengthened metal–oxygen bonding and reduced lattice disorder. Dielectric measurements demonstrate strong frequency dispersion governed by Maxwell–Wagner interfacial polarization and Koop's model, with enhanced dielectric constant and reduced high‐frequency loss for samples sintered at higher temperatures. AC conductivity follows Jonscher's universal power law, confirming hopping‐dominated charge transport associated with Fe2+/Fe3+ pairs at octahedral sites. The combined effects of Al3+‐induced lattice stabilization, Sn4+‐driven charge compensation, and sintering‐controlled microstructural evolution establish clear structure–property correlations, highlighting ZASFO ferrites as promising candidates for dielectric and multifunctional energy applications.

Tailoring the structural, magnetic, and dielectric properties of spinel ferrites through cation substitution is crucial for high-frequency electronics and electromagnetic interference (EMI) suppression. In this work, Zn0.5Ni0.5-xCuxFe2O4 (x = 0.00—0.50) ferrite nanoparticles were synthesized via the sol–gel auto-combustion method, and the influence of Cu2+ substitution on their structural, magnetic, dielectric, and permeability properties was systematically investigated. Rietveld-refined X-ray diffraction confirmed the formation of a single-phase cubic spinel structure, with a gradual increase in lattice parameter resulting from the incorporation of larger Cu2+ ions. FTIR and XPS analyses further verified successful Cu substitution while preserving the spinel framework. Magnetic measurements revealed a composition-dependent response, with the highest saturation magnetization of 83.33 emu/g at x = 0.20, attributed to optimized A–B superexchange interactions, whereas the lowest coercivity about 39.44 Oe at x = 0.4 indicated enhanced magnetic softness. Dielectric studies demonstrated Maxwell–Wagner interfacial polarization and reduced dielectric loss at higher frequencies. The x = 0.30 composition exhibited the most favorable permeability, combining high real permeability with low magnetic loss due to improved domain wall mobility and reduced magnetic anisotropy. These findings demonstrate that controlled Cu-induced cation redistribution effectively enhances the electromagnetic performance of Zn–Ni spinel ferrites, making them promising candidates for high-frequency inductive components and EMI shielding applications.

A novel soft-hard ferrite nanocomposite system composed of Ni0.55Cu0.2Zn0.25Fe2O4 (NCZFO) and SrFe12O19 (SFO) was synthesized for supercapacitor and hydroelectric cell (HEC) applications using physical mixing and one-pot sol-gel auto-combustion methods. XRD with Rietveld refinement confirmed high phase purity, while Raman and FTIR analyses revealed strong interfacial interactions between the ferrite phases. FE-SEM showed improved grain uniformity and reduced agglomeration in one-pot composites. Electrochemical studies demonstrated enhanced performance for one-pot samples, achieving a specific capacitance of 1067.2 F/g at 10 mV/s for x = 0.5, with 88% capacitance retention after 5000 cycles, indicating excellent long-term electrochemical stability. HEC measurements further showed superior activity for the one-pot x = 0.5 sample, delivering an open-circuit voltage of 1.52 V, short-circuit current of 45 mA, and power output of 68.4 mW. The improved performance is attributed to synergistic interfacial effects, oxygen vacancies, and efficient ionic transport facilitating spontaneous water dissociation and redox reactions. Density functional theory calculations supported the experimental findings by confirming favorable electronic structure and enhanced charge transport. These results highlight the importance of synthesis optimization and compositional tuning for multifunctional ferrite-based energy storage and conversion devices.

Despite extensive research on ferrite-based electrode materials, the development of high-surface-area NiFe2O4 with enhanced electrochemical performance and long-term cycling stability remains a challenge. In this study, NiFe2O4 spinel ferrite nanoparticles were successfully synthesized via the polyol method and systematically investigated for supercapacitor applications. Rietveld refinement confirmed the formation of a crystalline single-phase cubic spinel structure. Fourier transform infrared spectroscopy (FTIR), Raman, and X-ray photoelectron spectroscopy (XPS) analyses verified the characteristic bonding and chemical states of Ni and Fe within the ferrite lattice. Field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDAX) results revealed agglomerated spherical nanoparticles with uniform elemental distribution and a Ni/Fe ratio close to the theoretical composition. Brunauer–Emmett–Teller (BET) surface area of 147.857 m2/g and a pore volume of 0.555 cm3/g, confirming its mesoporous architecture. Electrochemical studies demonstrated a high specific capacitance of 676 F/g (0.676 F/cm2) at 1 mA/cm2 in 1 M KOH, along with excellent cycling stability, retaining 80.87

Nickel–Zinc (Ni-Zn) ferrites are promising magnetic materials for technological applications; however, further enhancement of their magnetic performance through cation substitution remains an important research challenge. In this study, cobalt-substituted Ni–Zn ferrites were synthesized using the sol–gel auto-combustion method to investigate the influence of Co2+ incorporation on their structural, microstructural, and magnetic properties. Thermogravimetric–differential thermal analysis (TG–DTA) was employed to determine the appropriate calcination temperature, while X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and magnetic measurements were used for comprehensive characterization. Rietveld-refined XRD patterns confirmed the formation of a single-phase cubic spinel structure (Fd–3 m) with high phase purity. A slight decrease in lattice parameter and porosity, accompanied by an increase in grain and particle sizes, was observed with increasing Co2+ content. Cation distribution analysis indicated the preferential occupation of octahedral (B) sites by Co²⁺ ions, leading to redistribution of Fe3+ ions and modifications in metal–oxygen bonding, as supported by FTIR results. Magnetic measurements revealed a significant enhancement in magnetic performance, with saturation magnetization increasing from 50.56 to 61.76 emu g⁻¹. The increases in remanent magnetization, coercivity, remanence ratio, and Bohr magneton number were attributed to enhanced ferrimagnetic ordering, cation redistribution, reduced spin disorder, and increased magnetic anisotropy. These findings demonstrate that Co2+ substitution effectively improves the structural and magnetic characteristics of Ni–Zn ferrites, making them attractive candidates for advanced magnetic applications.

Chromium-substituted dysprosium iron garnet nanoparticles with nominal composition Dy3Fe5-xCrxO12 (0.0 ≤ x ≤ 1.0) were synthesized via a sol–gel auto-combustion route to investigate the effect of Cr3 + substitution on the structural, vibrational, magnetic, and dielectric properties. X-ray diffraction confirmed the formation of single-phase cubic garnet for all compositions, with a systematic decrease in lattice parameter from 12.60 to 12.52 Å and a reduction in unit-cell volume from 2000 to 1963 Å3, indicating successful chromium incorporation into the host lattice. The crystallite size decreased overall from 47 to 37 nm, while intermediate compositions showed increased microstrain and dislocation density, revealing substitution-induced lattice distortion. FTIR and Raman analyses revealed shifts, broadening, and weakening of characteristic metal–oxygen vibrational modes, consistent with progressive local disorder and modification of FeO6/FeO4 polyhedra at higher Cr content. Magnetic measurements showed soft ferrimagnetic behavior for all samples, with saturation magnetization decreasing from 6.5 to 3.75 emu/g as Cr content increased, reflecting magnetic dilution and weakening of Fe–O–Fe superexchange interactions. Dielectric studies indicated enhanced low-frequency dielectric response together with suppressed dielectric loss, suggesting reduced conduction loss and improved dielectric stability after chromium substitution. Overall, the results demonstrate that Cr substitution effectively tailors the structure–property relationships in DyIG nanoparticles and provides a viable route for designing magneto-dielectric and multifunctional materials for high-frequency device applications.

This work establishes the critical solubility limit and magnetomechanical consequences of Yb3+ substitution in sintered cobalt ferrite ceramics, CoFe2-xYbxO4 (0 ≤ x ≤ 0.05), prepared by a tartrate-assisted sol–gel route followed by high-temperature sintering. A key outcome of the study is the identification of x = 0.025 as the maximum Yb3+ content that can be accommodated in the CFO spinel lattice without detectable secondary phase formation. X-ray diffraction and Raman spectroscopy confirm retention of the single-phase spinel structure up to x = 0.025, whereas higher Yb contents lead to the emergence of orthorhombic YbFeO3, revealing the structural solubility threshold. The results further show that low-level Yb3+ incorporation induces lattice expansion, local distortion, and magnetic tuning, while preserving phase purity and magnetic softness. Among all compositions, CoFe1.975Yb0.025O4 exhibits the most favorable low-field magnetomechanical response, with enhanced magnetostriction and strain sensitivity compared with unsubstituted CoFe2O4, making it particularly attractive for sensor-oriented applications. In addition, particle-size-controlled studies on this optimum composition reveal a strong microstructure–magnetism correlation, highlighting the role of crystallite size in governing magnetic behavior. These findings provide a clear composition–structure–property framework for Yb-substituted cobalt ferrites and identify CoFe1.975Yb0.025O4 as a promising rare-earth-modified magnetostrictive ceramic for low-field torque sensor and actuator applications.

Nd3+-substituted Ni0.7Zn0.3Cr0.5Fe1.5-xNdxO4 nanoferrites (0.00 ≤ x ≤ 0.05) were synthesized by the sol–gel auto-combustion route to examine how rare-earth substitution tunes the structural, dielectric, electrical, and magnetic characteristics of Ni–Zn ferrites. X-ray diffraction with Rietveld refinement confirmed the formation of a single-phase cubic spinel structure for all compositions. The larger ionic radius of Nd3+ compared with Fe3+ causes lattice expansion/local strain and indicates preferential incorporation into the octahedral B-site network, as also supported by the Bertaut-type cation-distribution analysis. TEM revealed a progressive reduction in particle size with increasing Nd content, consistent with the observed microstructural evolution. Elemental mapping/EDS supported a uniform spatial distribution of constituent elements across the investigated samples. FTIR spectra showed ferrite-related low-wavenumber metal–oxygen vibrational features, with band-shape modifications attributable to Nd-induced perturbation of the local bonding environment. Dielectric spectroscopy showed the expected dispersion of ε′ and tanδ with frequency; moreover, ε′ and dielectric loss decrease with Nd substitution, suggesting suppression of space-charge/interfacial polarization and reduced charge carrier mobility at grain boundaries. The frequency dependence of σac follows the typical ferrite response and is consistent with a hopping-assisted conduction mechanism; σac decreases with increasing Nd content, indicating inhibited hopping between localized states (e.g., Fe2+/Fe3+). Room-temperature M–H measurements confirmed soft ferrimagnetic behavior for all compositions, while the gradual reduction in saturation magnetization and coercivity with Nd incorporation is correlated with weakened A–B superexchange interactions, magnetic dilution, increased Yafet–Kittel spin canting, and modified anisotropy. Overall, Nd3+ substitution provides a viable pathway to tailor the microstructure and multifunctional response of Ni–Zn–Cr ferrites for high-frequency and low-loss magnetic/dielectric device applications.

Ba0.5Sr0.5Y1.0Fe11- xCox/2Tix/2O19 (x = 0.00-1.00) M-type hexaferrites were synthesized by a sol-gel autocombustion route followed by calcination at 1200 degrees C for 6 h to evaluate the Co-Ti-driven tuning of the magnetic properties and X-band (8-12 GHz) microwave attenuation. Rietveld-refined XRD confirmed the formation of the magnetoplumbite phase across the series, while refinement-based site allocation indicated Co incorporation mainly at the 12k sublattice and Ti preferential occupation of 4 f1/4f2 sites, with Y remaining fixed at the 2c site (Y1.0) for all compositions. Microstructural metrics extracted from XRD line-broadening show systematic lattice distortion with substitution: microstrain increases from 6.75 & times; 10-4 (x = 0.0) to 15.1 & times; 10-4 (x = 1.0), while the Williamson-Hall crystallite size increases from 16.90 to 23.28 nm. Concurrently, porosity decreases from 28.55% to 15.57%, indicating improved densification with Co-Ti content. Magnetic softening accompanies substitution, as reflected by a strong reduction in the anisotropy constant K1 from 1.02 & times; 105-3.15 & times; 104 erg cm- 3 and a decrease in Mr/Ms from 0.526 to 0.290, consistent with the reduced magnetocrystalline anisotropy and easier magnetization reversal at higher x. Microwave absorption, evaluated using ferrite-epoxy composites in the X-band, is maximized at intermediate substitution; the composition x = 0.75 exhibits an excellent minimum reflection loss of -45.04 dB at 9.208 GHz for 5.5 mm thickness, demonstrating highly efficient attenuation near 9-10 GHz, whereas excessive substitution shifts the matching condition toward higher frequency. The combined results show that maintaining a constant Y while tuning the Fe-sublattice chemistry via chargecompensated Co-Ti substitution provides a direct route for tailoring the anisotropy, microstructure, and impedance/loss balance of high-performance X-band microwave absorbers.

Phase-engineered garnet–perovskite oxide composites have attracted considerable attention owing to their tunable structural and magnetic properties for multifunctional applications. In this work, (1 – x)Eu3Fe5O12 – xLa0.5Dy0.5FeO3 (x = 0.00–1.00) composites were synthesized via a sol–gel auto-combustion method followed by high-temperature calcination. Rietveld-refined X-ray diffraction analysis confirmed the composition-dependent coexistence of cubic garnet (Ia-3d) and orthorhombic perovskite (Pbnm) phases with negligible secondary phases. Microstructural investigations revealed dense polycrystalline morphologies, while grain size evolution was influenced by the competing effects of diffusion-driven grain growth and grain-boundary pinning. Raman spectroscopy and X-ray photoelectron spectroscopy verified the structural integrity of both phases, the trivalent oxidation states of Eu, La, Dy, and Fe ions, and local lattice distortions associated with phase coexistence. Magnetic measurements revealed a progressive transition from ferrimagnetic to weakly canted antiferromagnetic behavior with increasing La0.5Dy0.5FeO3 content. The saturation magnetization decreased from 6.08 emu g-1 to 1.98 emu g-1, whereas the coercivity increased from 28.72 Oe to 146.18 Oe, reflecting enhanced magnetocrystalline anisotropy and domain-wall pinning associated with microstructural refinement and phase coexistence. The combined structural, spectroscopic, and magnetic analyses establish clear correlations between phase evolution, microstructure, and magnetic properties. To the best of our knowledge, this is the first systematic study of Eu3Fe5O12–La0.5Dy0.5FeO3 garnet–perovskite composites synthesized by the sol–gel auto-combustion route, providing insights into the design of phase-coexistent oxide ceramics with composition-tailored magnetic characteristics for advanced magnetic and spintronic devices.

Ce-substituted Fe-rich cobalt ferrite nanoparticles with the general formula Co0.9Fe2.1-xCexO4 (x = 0.0–0.10) were synthesized by a sol–gel auto-combustion route to investigate the interplay between lattice strain, elastic response, and magnetic anisotropy induced by rare-earth doping. X-ray diffraction combined with four independent strain–size models (Williamson–Hall, Size–Strain Plot, Halder–Wagner, and Nelson–Riley) confirmed the formation of a single-phase spinel structure and revealed that Ce incorporation simultaneously increases crystallite size ( 20–30 nm) and microstrain due to defect-mediated lattice distortion. FTIR-derived force constants and elastic moduli indicate progressive bond softening and porosity-driven reduction in effective stiffness with increasing Ce content. Magnetic measurements show a systematic enhancement of coercivity from 2.8 to 3.8 kOe and an increase in magnetocrystalline anisotropy, originating from Ce-induced lattice strain, defect-mediated domain-wall pinning, and modified spin–orbit coupling. In contrast, the saturation magnetization decreases due to dilution of B-site Fe3+ by non-magnetic Ce3+ and the consequent weakening of A–B superexchange interactions, consistent with Néel’s ferrimagnetic model. By correlating multiple strain-analysis models with elastic and magnetic parameters, this work establishes a unified structure–mechanics–magnetism framework for Ce-doped cobalt ferrites, which has not been previously reported. The combination of enhanced coercivity, tunable anisotropy, and defect-engineered elastic response highlights the potential of these materials for high-frequency magnetic devices, spintronic components, and multifunctional oxide-based applications.

Multifunctional lead-free magnetoelectric ceramics are highly desirable for next-generation sensing and energyharvesting applications. In this study, phase-coexistent (1-x)BaFe12O19-(x)La0.5Nd0.5FeO3 (x = 0.00-1.00) composites were synthesized via a sol-gel auto-combustion route followed by conventional sintering to engineer interfacial strain-mediated coupling. X-ray diffraction confirmed the coexistence of hexagonal BaFe12O19 (P63/ mmc) and orthorhombic La0.5Nd0.5FeO3 (Pbnm) phases without secondary impurities. A systematic lattice contraction of the hexaferrite phase (701.46 & Aring;3 to 646.44 & Aring;3) and non-monotonic crystallite size variation (32-55 nm) indicate composition-dependent interfacial strain. Microstructural analysis revealed controlled grain evolution governed by competing strain-induced inhibition and diffusion-driven growth. Raman and XPS studies confirmed structural distortion, mixed Fe2+/Fe3+ valence states, and oxygen vacancies contributing to enhanced interfacial coupling. Dielectric measurements exhibit Maxwell-Wagner type dispersion with high low-frequency permittivity, indicating strong interfacial polarization. The composite with x = 0.25 shows the highest magnetoelectric voltage coefficient of 99.8 mV/cm & sdot;Oe at room temperature under AC-DC magnetic excitation, attributed to optimized phase connectivity and efficient strain transfer. Ferroelectric P-E hysteresis loops display lossy behavior with a maximum saturation polarization of 6.54 mu C/cm2 and remanent polarization of 3.43 mu C/ cm2. The enhanced performance, achieved in a fully lead-free system, highlights the role of compositional tuning in maximizing interfacial coupling, making these composites promising for magnetic sensors, energy harvesters, and multifunctional ceramic devices.

Ni0.7Zn0.3Cr0.5Fe1.5-xErxO4 (x = 0.00–0.05) nanoferrites were synthesized by sol–gel auto-combustion to establish how low-level Er3+ substitution controls cation distribution, local bonding, dielectric transport, and ferrimagnetic ordering. Rietveld-refined XRD patterns confirmed single-phase cubic spinel formation, with Er3+ inducing slight lattice expansion, increased microstrain, and crystallite-size reduction from 20.3 to 12.7 nm. Bertaut-type cation-distribution analysis suggested a most probable average configuration, with a nearly stable tetrahedral arrangement, (Zn0.3Fe0.7)A, and preferential replacement of Fe3+ by Er3+ at octahedral B-sites. This B-site modification increased rB from 0.6533 to 0.6594 Å and ath from 8.3519 to 8.3682 Å, while tetrahedral bond parameters remained nearly unchanged. FTIR-derived force constants decreased with Er addition, indicating weakening of the metal–oxygen framework, particularly at octahedral sites. Elastic softening was confirmed by the decrease in C11 from 161.83 to 154.52 GPa and Young’s modulus from 47.62 to 45.47 GPa. Dielectric spectra followed Maxwell–Wagner-Koops behavior, while ac conductivity obeyed Jonscher’s power law, evidencing localized hopping transport. Magnetically, Ms decreased from 40.9 to 30.6 emu g-1, whereas Hc remained nearly constant near 750 Oe. The decrease in nB(exp) and increase in θYK confirmed enhanced B-sublattice spin canting. These results identify Er3+ substitution as an effective route for tuning octahedral-site chemistry, lattice rigidity, dielectric polarization, and magnetic exchange in Ni–Zn–Cr ferrites for high-frequency magneto-dielectric applications.