http://dspace.aiub.edu:8080/jspui/handle/123456789/1205 Tue, 31 Mar 2026 20:47:07 GMT 2026-03-31T20:47:07Z http://dspace.aiub.edu:8080/jspui/handle/123456789/2817 Title: Improved Matching Impedance Detected by Magneto-Dielectric Coupling in Bi1-xYxFeO3 ceramics for Wave Guided Antenna Authors: Parvez, Md. Masud; Hossain, Md. Sarowar; Hassan, Kamrul; Hossain, M. D.; Dutta, Sagar; Hasan, Md Razibul; Saha, Tusar; Bhuyan, M. D. I. Abstract: This study explores the structural and microstructural effects of Yttrium (Y3+) substitution at the Bi3+site in BiFeO3 (BFO), a prominent multiferroic material known for its ferroelectric, magnetic, and dielectric properties. Compositions of Bi1-xYxFeO3 with x =0, 0.05, 0.10, and 0.15 were synthesized using the sol-gel method. The X-ray diffraction (XRD) analysis confirms a rhombohedral perovskite structure (R3c mspace group) with reduced lattice parameters upon Y3+doping due to its smaller ionic radius. Microstructural analysis reveals a decrease in grain size and increased lattice strain, attributed to reduced diffusion rates and lattice distortion. The dielectric and magnetic properties are significantly improved, with increased impedance matching and reduced dielectric loss. Elastic and thermodynamic studies indicate a reduction in Young’s modulus, bulk modulus, and Debye temperature (θD)due to altered bonding configurations and increased bond lengths. Frequency-dependent an alyses demonstrated enhanced domain wall motion, reduced magnetic loss, and lower energy dissipation. These findings highlight the potential applications of Y3+-doped BiFeO3 as a promising multifunctional material for advanced applications in spintronics, sensors, microwave devices, electromagnetic interference shielding, and miniature antenna. Fri, 18 Apr 2025 00:00:00 GMT http://dspace.aiub.edu:8080/jspui/handle/123456789/2817 2025-04-18T00:00:00Z http://dspace.aiub.edu:8080/jspui/handle/123456789/2816 Title: Improved magneto-dielectric properties in Co substituted Cr ferrites for miniaturized antenna applications Authors: Sagor, Shohanur Rahman; Hossain, M. A.; Hossain, M. D.; Hossain, Md. Sarowar; Sikder, M. S. Abstract: The composition Cr(Fe1-xCox)2O4 with x =0.0, 0.1, 0.5, and 0.9 has been synthesized using the solid-state re action method followed by the double sintering technique of pre-sintering at 800 ◦C and sintering at 1332 ◦C. The structure and cationic distribution in the studied samples obtained by the Rietveld refinement of X-ray diffraction (XRD) patterns confirm a mixed spinel cubic structure of Fd3m space group, with a reduction in impurity phase (α-Fe2O3) as Co2+substitution increases. In addition, the scanning electron microscopy (SEM) of these samples indicates a decrease in grain size and porosities with higher Co content. The magnetic hysteresis measurement by a vibrating sample magnetometer (VSM) reveals that Co2+substitution at Fe3+enhances the magnetic properties, with maximum saturation magnetization (Ms)of ∼4.03×10 2 μB/F.U and coercivity (Hc) of ~102.1Oe observed for x=0.5. In addition, the frequency-dependent permeability (μ) improves with Co doping in Cr ferrite, and dielectric studies exhibit reduced loss tangent (tanδ)and enhanced dielectric quality factor (Qε). Finally, the matching impedance becomes stable across a broad frequency range (3kHz to 7MHz) with Z/η0≈0.75, resulting in the Co-substituted Cr ferrites as promising materials for miniaturized antenna applications including superior magneto-dielectric performance and eco-friendly composition. Tue, 11 Feb 2025 00:00:00 GMT http://dspace.aiub.edu:8080/jspui/handle/123456789/2816 2025-02-11T00:00:00Z http://dspace.aiub.edu:8080/jspui/handle/123456789/2815 Title: Enhanced Inductivity, Redox Potential, and Magneto-Dielectric Properties of SrFe12O19 Nano-Hexaferrite due to Cu and Gd Co-Substitution Authors: Islam, Md. Roni; Hossain, Md. Sarowar; Saha, Tusar; Khan, M. K. R.; Sarker, M. S. I. Abstract: The M−Type hexaferrites of composition SrFe12O19, Sr0.95Gd0.05Fe11.7Cu0.3O19, Sr0.95Gd0.05Fe11.4Cu0.6O19, and Sr0.95Gd0.05Fe11.1Cu0.9O19 have been synthesized through the conventional sol–gel method. The X-ray diffraction (XRD) patterns of the synthesized compositions confirm the hexagonal structure associated with the P63/mmc space group. The microstructure of these samples has been evaluated by transmission electron microscopy (TEM). In addition, the contribution of ferroelectric dipoles for all samples has been analyzed from the frequency-dependent dielectric constants and using the Cole-Cole relaxation and Jonscher power law model. The AC conductivity was measured for all studied samples in the frequency range of 100 Hz to 100 MHz. Additionally, optical absorbance spectra have been employed to estimate the band gap and redox potential of all samples. Notably, the phase angle predicts the exceptional inductive nature of Sr0.95Gd0.05Fe11.1Cu0.9O19 between 100 Hz to 100 MHz whereas the Sr0.95Gd0.05Fe11.7Cu0.3O19 functions as an inductor or capacitor, depending on the frequency. Wed, 29 Jan 2025 00:00:00 GMT http://dspace.aiub.edu:8080/jspui/handle/123456789/2815 2025-01-29T00:00:00Z http://dspace.aiub.edu:8080/jspui/handle/123456789/2814 Title: Computational and Experimental Approach to La3+ Doping at the B-Site of BiFeO3: Insights into BiFe0.90La0.10O3 multiferroic Authors: Dutta, Sagar; Hassan, Md. Rabiul; Bhuyan, M. D. I.; Tama, Angkita Mistry; Roy, Gourab Kumar; Saha, Tusar; Hossain, Md. Sarowar Abstract: The structure and microstructure of BiFeO3 and BiFe0.90La0.10O3 ratify a successful synthesis of the perovskite material associated with the R3c space group. The structural parameters have been obtained by the Rietveld-refinement of XRD data followed by the DFT calculation. The computed band structure manifests the existence of the up-spin indirect band gap (Eg) in both samples, along with a reduced Eg for La doping in BiFeO3 (2.73 eV). Apart from this, frequency-dependent dielectric properties of BiFeO3 and BiFe0.90La0.10O3 have been extensively studied theoretically as well as experimentally between 100 Hz to 100 MHz. Interestingly, the real part of the calculated dielectric function of the BFLO sample shifts from the larger positive values to the lower negative values with elevated frequency of the applied field. Therefore, experimental dielectric permittivity has been analyzed using the mathematical models of Logistic, Lorentz, and Polynomial functions. In addition, dynamic stability is reviewed by the phonon dispersion calculation that signifies entirely positive vibrational modes of both acoustic and optical phonons for BiFeO3, while BiFe0.90La0.10O3 exhibits two negative vibrational modes of acoustic phonons at -44.95 cm-1. However, the calculated Debye temperature (θD) for BFLO is ∼1214 K at 1000 K, which is ∼2 times higher than it is for BiFeO3 (∼608 K at 1000 K). Consequently, BiFeO3 and BiFe0.90La0.10O3 samples are categorized as weak ferromagnetic based on magnetic saturation (Ms) of 6.49 and 0.13 emu/g, respectively. Finally, BiFeO3 has been identified as ideal for energy storage electronic devices in higher frequency regions, while BiFe0.90La0.10O3 is more suitable for lower frequency applications. Mon, 31 Mar 2025 00:00:00 GMT http://dspace.aiub.edu:8080/jspui/handle/123456789/2814 2025-03-31T00:00:00Z