Sharif Digital Repository

In the magnetic recording media the switching field distribution (SFD) is an important micromagnetic characteristic curve. However, in general case, methods of assessing SFD have not presented a reasonable relation between the macroscopic measurements and the microscopic properties of the system. The degree of alignment of particles easy axis in a texture and the angular dependence of switching field are two fundamental factors for the distribution function. A technique for determining the switching field distribution curve due to these factors is reported. This technique is performed for textured iron fine particles and samples of CrO2 and γFe2O3 commercial tapes. The distribution differs... 

Fine Fe1-xCox grains with various values of × have been grown via the borohydride method in the presence of different magnetic fields, H0. In this method, the presence of magnetic moments at the bcc lattice sites of iron causes the formation of acicular single domain grains with a nearly 0.2 μm length. The magnetic field, H0, sets the magnetic moment of SD grains parallel to each other and forms some chains of these particles. This is equivalent to the presence of an effective internal field that increases the remanent magnetization, Mr. From the SW model point of view, the remanent magnetization of sample is determined by Boltzman distribution function at the two minimum energies. In fact,... 

Ca-doped Ni–Mg–Mn spinel ferrites with compositions of Ni0·5Mg0·3Mn0.2CaxFe2-xO4 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) were prepared via sol-gel auto-ignition technique. TGA/DTA, FTIR, XRD, FESEM, and VSM were employed to evaluate the thermal, spectral, structural, morphological, and magnetic features of Ca-doped Ni–Mg–Mn spinel ferrites. TGA/DTA curves show the weight loss in the sample. This weight loss was attributed to the oxidation and decomposition of the sample contents at a temperature of 500 °C. XRD reveals a single-phase structure of the Ni–Mg–Mn nano ferrites. A single-phase orthorhombic structure was confirmed for Ca-doped Ni–Mg–Mn ferrites. Structural parameters such as lattice... 

NMZ ferrites doped with rare earth having spinel composition Ni0.5Mn0.3Zn0.2X0.02Fe1.98O4, whereas X = Y, Pr and Gd were synthesized by sol gel auto-ignition method. XRD, FESEM, VSM and VNA were used to determine the phase, microstructural, magnetic and electromagnetic properties of rare earths doped NMZ ferrite. XRD analysis confirms the single phase of the rare earths doped NMZ ferrite. FESEM images shows Pr doped NMZ ferrite has less agglomerations and more porous structure as compared to NMZ and other rare earths doped NMZ ferrites. Magnetic analysis shows the enhancement in saturation magnetization and remanence with the doping of Y, Pr and Gd in NMZ ferrite. Dielectric properties were... 

In this study, an attempt has been made using different concentrations of rare-earth (RE) elements Yb, Gd in Ni–Zn spinel ferrite to examine the magneto-optical and electrical conductivity analysis of the prepared samples. RE doped Ni–Zn ferrite with composition Ni0.5Zn0.5YbxGdxFe2-xO4 (where, x = 0.00, 0.20, 0.40, 0. 60, 0.80 and 1.00) were prepared by one step sol-gel self-ignition approach. XRD and FESEM were used to examine the formation of a single-phase and variations in the grain size with the increasing contents of RE elements in Ni–Zn ferrite NPs. FTIR confirmed the vibrational studies of the RE doped spinel ferrite. The saturation magnetization, remanence, and coercivity elucidated... 

NMZ ferrites doped with rare earth having spinel composition Ni0.5Mn0.3Zn0.2X0.02Fe1.98O4, whereas X = Y, Pr and Gd were synthesized by sol gel auto-ignition method. XRD, FESEM, VSM and VNA were used to determine the phase, microstructural, magnetic and electromagnetic properties of rare earths doped NMZ ferrite. XRD analysis confirms the single phase of the rare earths doped NMZ ferrite. FESEM images shows Pr doped NMZ ferrite has less agglomerations and more porous structure as compared to NMZ and other rare earths doped NMZ ferrites. Magnetic analysis shows the enhancement in saturation magnetization and remanence with the doping of Y, Pr and Gd in NMZ ferrite. Dielectric properties were... 

In this study, an attempt has been made using different concentrations of rare-earth (RE) elements Yb, Gd in Ni–Zn spinel ferrite to examine the magneto-optical and electrical conductivity analysis of the prepared samples. RE doped Ni–Zn ferrite with composition Ni0.5Zn0.5YbxGdxFe2-xO4 (where, x = 0.00, 0.20, 0.40, 0. 60, 0.80 and 1.00) were prepared by one step sol-gel self-ignition approach. XRD and FESEM were used to examine the formation of a single-phase and variations in the grain size with the increasing contents of RE elements in Ni–Zn ferrite NPs. FTIR confirmed the vibrational studies of the RE doped spinel ferrite. The saturation magnetization, remanence, and coercivity elucidated... 

Co2+ and Cr3+-substituted SrBaCu2-xCoxCryFe28-yO46 X-type hexaferrite with x = y = 0, 0.1 to 0.5 (step = 0.1) were prepared through auto-combustion sol–gel method and sintered at 1250 °C for 5 h which was found from thermal analysis. The thermal investigation, phase detection, spectral, magnetic, and dielectric characteristics of the prepared composition were investigated by TGA, XRD, FTIR, VSM, and dielectric measurement. XRD patterns of the entire composition confirmed the development of a single phase of X-type structure. The enhancement in the lattice parameters and cell volume was observed by varying the Co–Cr concentration, attributed to the larger ionic radii substitution. FTIRspectra... 

We have studied the effect of negative chemical pressure in the RuGd 1.5(Ce 0.5-xPr x)Sr 2Cu 2O 10-δ with Pr content of 0.0 ≤ x ≤ 0.2. This is also investigated using the bond length results obtained from the Rietveld refinement analysis. The c parameter and cell volume increase with x for 0.0 ≤ x ≤ 0.15. The width of the resistivity transition also increases with Pr concentration, indicating higher inhomogeneity and oxygen deficiency. The difference in the ionic valences of Pr 3+,4+ and Ce 4+ causing different hole doping, the difference in the ionic radii, and oxygen stoichiometry affect the superconducting transition. The magnetoresistance shows a cusp around 135 K which lies between the... 

Co-Ce doped Ni nanocrystalline ferrites having composition Ni0.8Ce0.2CoxFe2-xO4 with x = 0.00, 0.25, 0.50, 0.75, 1.00 were fabricated by sol gel auto combustion method. Synthesized samples were investigated by thermal gravimetric and differential thermal analysis (TGA-DTA), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis (EDX) and vibrating sample magnetometer (VSM) to study the phase, vibrational modes, structure, surface analysis and magnetic properties respectively. Structural parameters (lattice parameters, cell volume, crystallite size and micro strains) were also calculated from XRD recorded data.... 

Pr doped spinel nanoferrites having following composition Cu Pr x Fe 2-x O 4 (x = 0, 0.25, 0.50, 0.75, 1.00) were synthesized using sol-gel route. Prosademium (Pr) which is a rare earth metal was doped to tailor the properties of the Cu spinel nanoferrites. Characterization tools such as FTIR, XRD, FESEM and VSM were employed to investigate the phase, absorption bands, structure, microstructure and magnetic properties. FTIR was used to see the absorption bands and force constants of the Pr doped Cu spinel nanoferrites. Crystallite size, lattice parameters, cell volume and micro strains were determined from XRD data. Bulk density, X-ray density and porosity of the Pr doped Cu spinel... 

Copper (Cu) substituted Co–]Ce nanoferrites with nominal composition of Co 1-x Cu x Ce 0.05 Fe 1.95 O 4 (x = 0.00, 0.25, 0.50, 0.75, 1.00) were prepared by sol-gel route. The sintering of the Cu doped Co–]Ce nanoferrites was done at 700 °C to investigate the desired properties of the Cu doped Co–]Ce nanoferrites. The combination of transition metal (Cu) and rare earth (Ce) were employed to tailor the characteristics of the spinel ferrites. The constant ratio of rare earth and systematic doping of Cu in Co ferrite was incorporated to see the effects of these ions in spinel ferrite. FTIR, FESEM, XRD and VSM were used to study the vibrational bands, phase, morphology, structure and magnetic...