Homogeneous Ferrite Research Articles

Origin of magnetocapacitance in chemically homogeneous and inhomogeneous ferrites.

The present work mainly focuses on the magnetodielectric (MD) effect in polycrystalline Ni0.9-yCuyZn0.1Fe1.98O3.97 (y = 0, 0.1, 0.2, 0.3, 0.4, 0.5) ferrite synthesized by a solid-state reaction method. Sintered samples showed the formation of CuO-rich grain boundary segregation for y≥ 0.2. The appearance of segregation made the present material chemically inhomogeneous and electrically heterogeneous. A negative MD response was observed in homogeneous ferrite for y = 0 and 0.1 due to lattice distortion (an intrinsic effect), whereas a positive MD response occurs in chemically inhomogeneous segregated ferrite (y≥ 0.2) due the collective effects of Maxwell-Wagner (MW) polarization with intrinsic magnetoresistance (an extrinsic effect).

Mechanisms of phase formation along the synthesis of Mn–Zn ferrites by the polymeric precursor method

Considering the wide application of crystalline Mn–Zn ferrites microparticles, understanding synthesis routes that allow the achievement of such materials is a constant need. In this work, Mn–Zn ferrites, Mn(1−x)ZnxFe2O4 (0.15≤x≤0.30), were synthesized by the polymeric precursor method in well-controlled steps and the mechanisms of phase formation under different thermal treatments were studied. Such investigation was performed by means of thermal analysis (TG/DTA), synchrotron X-ray powder diffraction (SXPD) (including in-situ and anomalous scattering experiments) and scanning electron microscopy (SEM). The ferrite precursor powders present the spinel as single crystalline phases whose cell parameters increase as Mn is substituted by Zn, indicating possible Fe deficiencies into the structure. The crystallization degree of these samples is also affected by the Mn substitution and reaches a maximum for x=0.25. Further thermal treatments in air at 700°C and 1100°C lead to additional events also related to the Zn content, such as carbonates elimination and crystallization of the contaminant phase hematite. Thermal treatments under N2 atmosphere at 700°C allow the achievement of powders with only the spinel phase, especially for x=0.25 for which highly crystalline and homogeneous ferrite is obtained despite the Fe deficiency determined by anomalous scattering SXPD. Finally, thermal treatments at 1100°C under N2 atmosphere jeopardize the stability of the spinel structure and lead to hematite precipitation.

Microstructure study and hyper frequency electromagnetic characterization of novel hexagonal compounds

The physical characteristics and preparation of novel Z-type hexagonal compound, which have iron deficient composition of Ba3Co2(0.8−x)Cu0.4Zn2xFe23.5O41 (x≤0.30), was investigated. The results show that Zn has little effect on the morphology of compact and homogeneous ferrites with average 10–15μm of lathy grain size, but make the formation temperature range narrow. In the range of Zn incorporation, the hexagonal cell lattice parameters (a and c) of ferrites reserve stable. However, the key magnetic and electrical properties, such as initial permeability, quality factor, resistivity, dielectric constant and magnetic hysteresis as well as Curie temperature were also characterized. The mechanisms involving in generating these variations were also discussed in this paper.

Investigations into Phase Formation of Decomposed Ni0.5Zn0.5Fe2(C2O4)3 6 H2O Solid Solution Oxalates

AbstractHomogeneous solid solution oxalates of Ni(II)‐, Fe(II)‐ and Zn(II) were prepared by coprecipitation from metal acetate solution with oxalic acid. Using Mössbauer spectroscopy, XRD, magnetic measurement and IR‐spectroscopy, the thermal decomposition of Ni0.5Zn0.5Fe2(C2O4)3 · 6 H2O and the formation process of Ni0.5Zn0.5Fe2O4 were investigated.At temperatures between 300 and 400 °C the thermal decomposition of the Ni–Zn–Fe solid solution oxalates leads to ferrites of spinel structure, but areas with a different content of Ni and Zn are provable by Mössbauer spectroscopy. After tempering at 750 °C homogeneous ferrites arise.

Propagation in Arbitrarily Magnetized Ferrites Between Two Conducting Parallel Planes

The electromagnetic waves propagating in arbitrarily magnetized homogeneous ferrites between two perfectly conducting parallel planes have been investigated by using the operational calculus method. The discrete propagation constants and the eigenvalues are to be determined from an algebraic equation of the fourth order and a determinantal equation derived from the boundary conditions. The hybrid modes thus found degenerate to the solutions already found for the particular cases of longitudinally and transversely (parallel and perpendicular to boundaries) magnetized ferrite cases.