X-ray, IR and SEM studies on some Li-Cd ferrites

Lithium-Cadmium ferrites with general formula Li0.5-x/2 Fe2.5-x/2 Cdx O4 (with x = 0,0.1,0.2....,0.7) were prepared by standard ceramic method. X-ray diffraction studies confirms single phase formation and lattice parameters were calculated. The crystal structure is cubic and lattice parameter increases with increasing Cd content. The infrared absorption (IR) spectra of all the samples were recorded in the range 200-800 cm-1 at room temperature in the KBr medium. Lithium ferrite shows four principal bands and some shoulders have been observed. The force constants Kt and Ko were calculated using Waldron's analysis. Scanning electron microscopy studies shows increase in grain size up to x = 0.1 and then the grain size decreases with increase in cadmium content.

Magnetic Study on Divalent Ion Substituted Barium Hexaferrites

Magnetic properties of Co, Ni and Zn substituted barium hexaferrite (BaM) samples prepared by solid state ceramic method were studied. Saturation magnetisation were found higher for Zn-substituted BaM, whereas, coercivity is higher for Co2+ and Ni2+ ion substituted samples. Anisotropy field for all substituted samples was calculated by the law of approaching saturation. Remanence, squareness and thermomagnetic plot suggest Zn2+ ions restricts the magnetic interaction of various sites in BaM.

Effects of Ga Substitution on Micromorphology and Static Magnetic Properties of Self-Biased M-Type Sr Hexaferrites

The Sr hexaferrites with chemical formula Sr0.4La0.3Ca0.3Fe11.85-xGaxCo0.15O19 (x = 0.0 — 1.4) were manufactured by traditional ceramic method. The affect of Ga substitution on static magnetic properties and micromorphology of M-type Sr (SrM) hexaferrites have been presented in detail. In accordance with the experiment results, as Ga-substituted content x rises up from 0.0 to 1.4, all SrM hexaferrite samples are magnetoplumbite hexagonal structure. The difference between radius of Fe3+ and Ga3+ ions leads to the decrease of lattice constants. As the amount of Ga substitution x increases from 0.0 to 1.4, the 4πMs and 4πMr presents a trend of increasing, but the Hc shows the opposite trend. K1 and Ha of all samples are higher than 2.5×105 J/m3 and 21 kOe respectively, which manifests all samples possess the strong uniaxial anisotropy. The materials discussed in this paper possess huge potential in the application of high frequency self-biased microwave devices.

Effect of the Glycine Treatment on Synthesis and Physicochemical Characteristics of Nanosized Ni-Mn Mixed Oxides

Magnetic Ni-Mn mixed oxides based on nanoparticles (NPs) have been developed at 700 °C using a ceramic method and a glycine-assisted auto combustion path. The thermogravimetry–derivative thermogravimetry (TG—DTG), infrared radiation (IR), X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and high resolution transmittance electron micrographs (HRTEM) techniques have been used to characterize as synthesized nanomaterials by evaluating their thermal behavior, structure, distinguishing the components and establishing the morphology. A vibrating sample magnetometer has been used to estimate the magnetic properties of the materials (VSM). The analyses indicate that using a glycine-assisted auto combustion method resulted in formation of cubic spinel NiMn2O4 NPs as a single phase. The ceramic process, from the other side, led to the development of Mn2O3/NiMnO3/NiMn2O4 nanocomposite. The resulting particles being polycrystalline, including average sizes ranging from 10 to 80 nanometers. The prepared NiMn2O4 NPs showed room-temperature ferromagnetism, with an optimal saturation magnetization value of 5.0216 emu/g, according to the magnetic measurement.

Investigation of Ferrimagnetic Sr-hexaferrite Nanocrystals for Clinical Hyperthermia

Sr-hexaferrite samples were produced via the conventional ceramic method. X-ray diffractometry (XRD) patterns confirmed the single nanocrystal phase as Sr-hexaferrite where any pattern peaks of unreacted Fe2O3 phase were not detected. The mean crystallite size values were determined to be 44.12±3.4nm and 41.2±3.2nm for SHF-O1 and SHF-O2, respectively. The chemical bonding peaks of our sample indicated that the structure of Sr-hexaferrite formation was confirmed by FTIR spectra result. Scanning electron microscopy (SEM) images indicated clearly observed porosity regions with relative densities as high as 94% and 87% for SHF-O1 and SHF-O2 samples.The vibrating sample magnetometry (VSM) of each sample at 2K and under a magnetic field of 10 kOe yielded saturation magnetizations, Ms of 93.5 and 94.1 emu/g; remanence values, Mr of 76.4 and 67.8 emu/g for SHF-O1 and SHF-O2, respectively. The magnetization loops of both samples indicated a soft ferrimagnetic behaviour in which the saturation magnetizations were higher than those measured at room temperature in the previous studies. The coercivities, Hc were measured to be 150Oe for both samples. The squareness values, SQR (Mr/Ms) were measured to be high, approximately 0.82 and 0.72 for SHF-O1 and SHF-O2, respectively. Depending on the adequate values of magnetization and coercivity along with small mean crystallite size and low porosity values of the obtained Sr-hexaferrite samples, we estimate that these samples are likely to be evaluated further for the potential use as thermoseeds in the field of clinical hyperthermia.

Effect of Polaron Hoping on Electrical Properties of Magneto Electric Composites

Co0.7-xNixMn0.3Fe2O4 (CNMFO) ferrites with x = 0.00, 0.05, 0.10 and 0.15,PbZr0.52Ti0.48O3(PZT) ferroelectric and 30% CNMFO – 70% PZT magneto electric(ME) composites were synthesized by double sintering ceramic method. XRD confirms pure phase formation for all compositions of ferrite, ferroelectric and ME composites. All compositions of ferrites, ferroelectric and ME composites show negative temperature coefficient of resistance (NTCR) confirming the semiconducting behavior, though the conduction mechanism is quite different than known semiconductors such as, silicon and germanium. The conduction, due to electron hoping in semiconductors against polaron hoping in ferrites is explained. The effect of cation distribution on resistivity of ferrite phase is also discussed. Thus, effect of polaron hoping and cation distribution on resistivity and dielectric constant of ferroelectric and ME composites has been discussed. Effective resistance of ME composites due to combined resistance of the constituent phases has also been studied.