Complex permeability of Fe-deficient Ni–Cu–Zn ferrites

Fe-deficient Ni-Cu-Zn ferrites with composition Ni0.28Cu0.10Zn0.62O(Fe2O3)(1-x), where x = 0.00, 0.02, 0.04, 0.06, and 0.08 were prepared by the double sintering ceramic technique. Real part of the initial permeability mu', Curie temperature T-c, imaginary part of the initial permeability mu '', relative quality factor (Q-factor) of the samples were elaborately discussed as a function of frequency and temperature with increase of Fe-deficiency during the heating and cooling cycles. The temperature dependence of the imaginary part of the complex permeability curves are very interesting to note that there is a peak value of mu '' at particular temperature which corresponds to the T-c because at this temperature the samples might be in complete spin disorder. This reflects that at T-c, a ferrimagnetically ordered state over comes KBT and becomes comparable with mu H-0 where the loss becomes maximum. Results of heating and cooling cycles were found to be very close to each other. The small difference during heating and cooling process might arise due to the thermal hysteresis which is accumulated in this work. In our study, it was noticed that the resonant frequency and T-c increases first with the increase in iron deficiency and decreases after it takes a maximum at x = 0.06

Effect of salinity on dynamic dielectric properties of Sundori wood of Bangladesh

The dynamic dielectric properties of Sundari wood have been investigated for their dependence on saline content and various thicknesses of wood slice. Measurement of capacitance and loss tangent have been carried out in the range from 1 kHz to 13 MHz (Agelent 4192 A LF) at room temperature. The calculated values of the dielectric constant at oven-dry condition were found to be between 2.69 to .086 and was increased with the wood slice thickness. These results were varied with their saline content. The introduction of salt ions into the Sundari wood matrix increases the dielectric constant by a factor of two

Study of structural and magnetic properties of Sr-hexaferrites using additives

M-type strontium hexaferrites of composition (SrO)1-x (La2O3)x 5.7 Fe2O3, where x = 0.00, 0.04, 0.08 were successfully prepared by standard ceramic technique using magnetite from Cox’s Bazar beach sand. The influence of the composition on both the structural and magnetic properties of M-type Sr-hexaferrites with substitution of Sr2+ by La2O3 of various samples were investigated. The effect of simultaneous addition of CaO and SiO2 on the structural and magnetic properties of the hexaferrites sintered at different temperatures was also studied. The prepared samples were studied by measuring density, X-ray density, porosity, lattice parameters, unit cell volume, Curie temperature and X-ray diffraction (XRD) technique. It has been observed that the structural and magnetic properties of the sintered Sr-hexaferrites increases significantly with the addition of La2O3 ¬ and (CaO + SiO2) and sintering temperature

Order-disorder phase transition and lattice parameter of Ni–Pt alloys

In this paper order-disorder phase transition of undoped Ni0.5Pt0.5 alloy and doped with Fe and Co with compositions Ni0.45Fe0.05Pt0.5 and Ni0.45Co0.05Pt0.5 respectively were studied by X-ray diffraction (XRD) method. It has been observed that Ni–Pt alloys undergo disorder-order transformation at high temperature from fcc (face centered cubic) structure to fct (face centered tetragonal) phase. Lattice parameters of the three disordered and three-ordered Ni–Pt and doped alloys were determined. Disordered state of Ni–Pt alloy shows fcc structure with lattice parameter of a = 3.7468 Å, while ordered one is fct having a = 3.8187 Å and c = 3.6028 Å with c/a ratio of 0.943. A slight increase of c/a ratio has been observed for Fe and Co doped alloys. The lattice parameters of the ordered fct phase of Ni0.45Fe0.05Pt0.5 and Ni0.45Co0.05Pt0.5 are a = 3.8141 Å, c = 3.6069 Å and a = 3.8174 Å, c = 3.6154 Å with c/a ratio of 0.945 and 0.947 respectively. Fe and Co doped Ni–Pt alloys has been found to be multiphased in contrast to the undoped counterpart. The corresponding N–R functions for each reflection planes have been reported as well

Magnetization and magnetic behavior of Ni1-xCdxFe2O4 ferrites

This article describes the experimental investigation on the magnetization behavior of Ni1-xCdxFe2O4 ferrites for x greater than or equal to 0.0 & less than or equal to 0.8 prepared by conventional ceramic method. Magnetic properties have been measured as a function of field and temperature using vibrating sample magnetometer and SQUID magnetometer. Saturation magnetization at 20 K increases with Cd-content up to x = 0.5 and decreases thereafter. Neel’s two sublattice collinear model is applied for the initial rise of the magnetization up to x less than or equal to 0.5 and beyond that three sublattices non-collinear model proposed by Yafet-Kittel are predominant. This indicates the appearance of spin canting structure in Ni1-xCdxFe2O4 ferrites with higher Cd-content. Sample with x = 0.8 shows anomalous temperature dependent magnetic ordering on applied magnetic field. Low field (5 Oe) magnetization shows antiferromagnetic ordering while the ferromagnetic ordering has been found to be dominant with the high field (1 T). That is the magnetic ordering of Ni1-xCdxFe2O4 is dependent on the strength of applied field

Structural effect on Magneto-electric properties in (1-x) BiFe0.9La0.1O3 + xNi0.6Zn0.4Fe1.94V0.06O4 composites

Enhancement of magnetic as well as electric properties in BiFe0.9La0.1O3 (BLFO) with the addition of Ni-Zn ferrite have been studied on the compositions (1-x)BiFe0.9La0.1O3 + xNi0.6Zn0.4Fe1.94V0.06O4 (where, x = 0, 0.1, 0.2, 0.3, 0.5, 0.7 and 1.0). The samples were synthesized by the conventional ceramic methods sintered at 850 °C for 2 h. XRD studies revealed a normal distorted rhombohedral phase (R3c space group), cubic phase (Fd-3 m space group) and some impurity phases like Bi2Fe4O9 and Bi25FeO39 in the synthesized composites. The addition of Ni0.6Zn0.4Fe1.94V0.06O4 (NZVFO) successfully eliminated Bi25FeO39 phase from the derived composites. The average grain sizes (Dg) were estimated from FESEM images and found to decrease with the increase of NZVFO content in the samples. There is a large increment in saturation magnetization (MS) from 0.1 emu/g to 50.5 emu/g for adding NZVFO in BLFO. The frequency-dependent magnetic permeability μ and dielectric constant ε and dielectric loss tanδε have been measured with an impedance analyzer. The addition of NZVFO results in decreasing the permittivity ε' and dielectric loss (tanδε). The composites with 0.7 NZVFO addition shows a stable matching impedance Z/η0≈0.5 over a wide frequency range (5–70 MHz), demonstrating its possible applications in miniaturizing devices such as microwave antenna

Thermal hysteresis of permeability and transport properties of Cu Substituted Ni0.28Cu0.10+ x Zn0.62– x Fe1.98O4 ferrites

Cu Substituted Ni–Cu–Zn ferrites of Composition Ni0.28Cu0.10+ x Zn0.62– x Fe1.98O4 have been prepared by the standard double sintering ceramic technique. The samples were sintered at 1150 C for 3 hours in air. The analysis of XRD patterns indicates that the samples have the single phase cubic spinel structure. The lattice constant is found to decrease linearly with increase in Cu2+ ion concentration obeying Vegard's law. The initial permeability (μ i ) of the Ni–Cu–Zn ferrites exhibits thermal hysteresis when the temperature is cycled from above the Curie temperature Tc to below. The sharp decrease of μ i at T = Tc indicates the sample's good homogeneity. The Curie temperatures, Tc of the studied ferrite samples were determined from the μ i – T curves where the Hopkinson type of peak at the Tc has been observed with the manifestation of a sharp fall in permeability. The Tc is found to increase with increasing Cu-content. DC electrical resistivity increases significantly with the increase of Cu-Content. The ac resistivity (ρ ac ) and dielectric constant (ε′) of the samples are found to decrease with increase in frequency, exhibiting normal ferrimagnetic behavior