[en] The ultrasonic velocity and attenuation of 1 MHz longitudinal and transverse waves have been measured on ploycrystalline YIG, with mean grain size ranging from 3 to 30 μm. The velocity and attenuation have been measured in the temperature range of 300-560 K using the pulse transmission method. The room-temperature velocity is slightly sample dependent and decreases smoothly with increasing temperature, except near the Curie temperature T_C, where a small anomaly is observed. The room-temperature attenuation α₁ is relatively more sample dependent and its temperature variation exhibits a broad maximum around 400 K, and a very sharp maximum just before T_C. The above observations were carried out in the demagnetized state; the application of a 2 kOe magnetic field allowed reaching the saturated state at any of the measuring temperatures. The observed anomaly near the T_C is explained with the help of temperature variation of magneto-crystalline anisotropy constant k₁

[en] Polycrystalline samples of Mn (1%) added MgCuZn ferrites were prepared by conventional solid-state reaction method. Samples were sintered at different temperatures in the range of 975–1175 °C for 10 h. The longitudinal wave velocity (V_l) and shear wave velocity (V_s) were measured using ultrasonic pulse transition technique. The values of V_l and V_s were increased with an increase in sintering temperature. Using these values of velocities; longitudinal modulus, rigidity modulus, bulk modulus, Young's modulus and Poisson's ratio were calculated. The values of elastic moduli were increased with an increase in sintering temperature. Poisson's ratio was constant for all the samples. The elastic moduli of samples were corrected to zero porosity using well-known models. Debye temperature and average sound velocity were calculated. Debye temperature and average sound velocity were increased with an increase in sintering temperature. A linear relationship between Debye temperature and average sound velocity was observed. These results suggest that sintering condition has a prominent effect on the elastic properties. - Highlights: • The bulk density increases and porosity decreases with an increase in sintering temperature. • The elastic moduli of samples increase with an increase in sintering temperature. • Poisson's ratio is constant for all the samples. • A linear relationship between average sound velocity and Debye temperature is observed

[en] MgCuZn ferrite and BaTiO₃ powders with the crystallite sizes 88 nm and 82 nm were prepared using a high energy mechanical milling and sintering method. The prepared powders were characterized using X-ray diffractometer (XRD), Fourier transform infrared spectrometer and scanning electron microscope (SEM). The nanopowders were mixed to obtain the composites with composition xBaTiO₃+(1−x)Mg_0.48Cu_0.12Zn_0.4Fe₂O₄ (where x=0–1) using a mechanical milling. The presence of ferroelectric (BaTiO₃) phase and ferrimagnetic (MgCuZn ferrite) phase has been confirmed using XRD and SEM. Ferroelectric hysteresis loops and magnetic hysteresis loops have been recorded at room temperature. In polarization–electric-field curves (P–E), the remanent polarization and coercive fields display little asymmetry. When the amount of ferrite phase is increased, the ferroelectric coercive field also increases. The saturation magnetization decreases with an increase of phase fraction of BaTiO₃, because the interaction between magnetic grains is weakened by the existence of nonmagnetic (ferroelectric) phase that is distributed in the magnetic phase. The electrical properties were measured on the composites at 1 MHz. The static magnetoelectric (ME) voltage coefficient (dE/dH)_H was measured by change in ME output voltage with respect to dc bias magnetic field at a constant applied magnetic field. - Highlights: • Mg_0.48Cu_0.12Zn_0.4Fe₂O₄+BaTiO₃, nanocomposites are prepared by mechanical milling. • The existence of ferroelectric and ferromagnetic phases in the samples is confirmed by XRD and SEM. • The nanocomposites exhibit ferroelectric and magnetic hysteresis loops at room temperature. • The electrical properties of the composites are measured at 1 MHz. • The static magnetoelectric voltage coefficient is measured at a fixed applied magnetic field

[en] For the first time the electrical conductivity of polycrystalline mixed Ba-Sr ferrites is studied as a function of composition and of temperature. X-ray analysis and Seebeck coefficient studies are also carried out so that the conductivity of these mixed ferrites can be discussed. All the ferrites exhibit a transition with a change in the slope of the conductivity (lg σ) versus temperature (10³/T) curve. It is found that the activation energy in the paramagnetic region is higher than that below the transition temperature. (author)

[en] Polycrystalline samples of Mn (1 %) added MgCuZn ferrites have been prepared by conventional solid-state synthesis. Samples have been sintered at different temperatures in the range of 975-1175 °C for 10 h, followed by characterization by X-ray diffraction (XRD) and field emission scanning electron microscope. XRD results reveal that all samples are single phase with spinel structure. Lattice constant increases slightly with increase in sintering temperature. Bulk density and grain size increase with increase in sintering temperature, from 4.61 g/cm³ and 2.2 μm at 975 °C to 4.99 g/cm³ and 8.8 μm at 1175 °C. DC electrical resistivity decreases and dielectric constant and initial permeability increase with an increase in sintering temperature. These results suggest that sintering temperature has a prominent effect on the electrical properties. (author)

[en] Conductivity measurements are carried out in pre-quenched and quenched NaYF₄ pellets to understand the transport properties and the dynamic behaviour of the mobile fluoride ion at temperatures between 350 and 700 K. The activation energies for three distinct temperature regions have been calculated and discussed

[en] The temperature dependence of the thermoelectric power theta of unquenched and quenched polycrystalline NaYF₄ samples is investigated in order to understand the transport properties clearly. After increasing of theta with temperature up to 365 K the curve saturates

[en] Several characteristics of fission accompained by long range alpha particles (LRA) have been studied in the thermal neutron induced fission of ²³⁵U. The dependence of different quantities in LRA fission on the fragment mass ratio, LRA energy and the total kinetic energy of the fission fragments has been investigated. It is seen that the most probable energy of LRA increases significantly for near symmetric mass divisions. The total kinetic energy for all mass ratios in LRA fission is found to be (2.6 -+ 0.7) MeV larger than that in binary fission. The difference in the total kinetic energies in LRA and binary fissions is seen to be dependent on mass ratio. This result may suggest that the scission configuration in LRA fission is different for different mass ratios. Correlations between the fission fragment and LRA energies have been studied for several mass ratios. The present results are discussed to arrive at a better understanding of the scission configuration in the fission accompained by LRA emission. (author)

[en] Nanocrystalline Barium Ferrite (BaFe₁₂O₁₉) have been prepared by microwave sintering method at different sintering temperatures. The prepared samples were characterized by X-ray diffraction. The crystalline size of these samples has been varies from 40 nm to 60nm. The lattice constant and bulk density of these samples increase with an increase of sintering temperature. The temperature variation of electrical conductivity (σ) of these samples was measured by two probe method. The electrical conductivity in these ferrites have been explained on the basis of hoping mechanism. The plots of log σ T versus 103 /T are show a transition near the Curie temperature. The activation energy in the ferromagnetic region is in general less than that in the paramagnetic region. The dielectric properties such as dielectric constant (ε′), dielectric loss tangent (tan δ). The dielectric constant and loss tangent are found to be decreasing with the increase in frequency. The dielectric properties have been explained on the basis of Maxwell-Wagner’s two-layer model and hopping of the charge. The magnetic properties such as initial permeability (µi) and relative loss factor (RLF) have been investigated as a function of frequency in the range 75 kHz to 30 MHz. (author)

[en] The nanocrystalline MgCuZn ferrites with particle size (∼30 nm) have been synthesized by microwave-hydrothermal (M-H) method at 160 deg. C/45 min. The powders were densified at 750-900 deg. C/30 min using microwave sintering method. The sintered samples were characterized using X-ray diffraction and scanning electron microscope. The grain sizes of the sintered samples are in the range of 60-80 nm. The ultrasonic velocities have been measured on MgCuZn ferrites using the pulse transmission method at 1 MHz. The ultrasonic velocity is found to decrease with an increase of temperature. A small anomaly is observed around the Curie temperature, 520 K. The anomaly observed in the thermal variation of longitudinal velocity and attenuation is explained with the help of magneto-crystalline anisotropy constant.