V. R. K. Murthy

Bio: V. R. K. Murthy is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Dielectric & Rietveld refinement. The author has an hindex of 27, co-authored 162 publications receiving 2595 citations. Previous affiliations of V. R. K. Murthy include VIT University & Indian Institute of Science.

Microwave conductivity studies on some semiconductors

Abstract: The cavity perturbation technique is employed for the characterisation of semiconductors at microwave frequency for its conductivity. Temperature variation of microwave conductivity studies provide the information regarding the band gap, scattering parameter and impurity ionization energy. Change in the real part of the dielectric permittivity with conductivity indicates the change in the momentum relaxation time.

Two-dimensional microwave band-gap structures of different dielectric materials

Abstract: We report the use of low dielectric constant materials to form two-dimensional microwave band-gap structures for achieving high gap-to-midgap ratio. The variable parameters chosen are the lattice spacing and the geometric structure. The selected geometries are square and triangular and the materials chosen are PTFE (e = 2.1), PVC (e = 2.38) and glass (e = 5.5). Using the plane-wave expansion method, proper lattice spacing is selected for each structure and material. The observed experimental results are analyzed with the help of the theoretical prediction

Excess Dielectric and Thermodynamical Studies on Hydrogen Bonded Binary Mixtures of Propan-1-ol with Methyl and Ethyl Benzoates

Abstract: The molecular interactions between the polar systems propan-1-ol with alkyl benzoates (methyl benzoate and ethyl benzoate) for various mole fractions at different temperatures were studied by determining the dielectric permittivity using - LF impedance analyzer, microwave bench and Abbe's refractometer in radio, microwave and optic frequency regions respectively. Dipole moment, excess dipole moment, excess Helmholtz free energy, excess permittivity, relaxation time, excess inverse relaxation time and excess thermodynamical values are calculated using experimental data. Hamiltonian quantum mechanical calculations are performed on both pure and equimolar binary systems of propan-1-ol with alkyl benzoates for the measurement of dipole moment using PC Spartan and Argus lab Modeling softwares and these theoretical values are in good agreement with the experimental values. These studies can give information on its structure and interaction.

Dielectric relaxation studies of acetonitrile/propylene glycol and their binary mixtures

Abstract: Dielectric relaxation spectra in the frequency range 0.02 < ν/GHz < 20 have been collected for propylene glycol (PG), acetonitrile (AN) and their binary mixtures between 303 K-323 K. The average relaxation times have been calculated by the Cole-Davidson and Cole-Cole relaxation models. The experimental determined values of static dielectric permittivity (e 0 ), relaxation time (τ), excess permittivity (e E ) and excess inverse relaxation time (1/τ) E show smooth temperature dependence. The larger relaxation time values of propylene glycol when compared to acetonitrile are due to the co-operative process of multimers with O-H-O linkage and also the steric hindrance behavior phenomena. The activation entropy (Δ S* ), activation enthalpy (Δ H* ), Kirkwood correlation factor ( g f ), Helmholtz energy (Δ F E ) parameters have also been determined for propylene glycol and acetonitrile and the results have been correlated.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Photonic crystals

Abstract: The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

Ferromagnetic materials

Abstract: In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Magnetic and electric properties of transition-metal-doped ZnO films

Abstract: 3d-transition-metal-doped ZnO films (n-type Zn1−xMxO (x=005–025): M=Co, Mn, Cr, Ni) are formed on sapphire substrates using a pulsed-laser deposition technique, and their magnetic and electric properties are examined The Co-doped ZnO films showed the maximum solubility limit Some of the Co-doped ZnO films exhibit ferromagnetic behaviors with the Curie temperature higher than room temperature The magnetic properties of Co-doped ZnO films depend on the concentration of Co ions and carriers

Wide band gap ferromagnetic semiconductors and oxides

Abstract: Recent advances in the theory and experimental realization of ferromagnetic semiconductors give hope that a new generation of microelectronic devices based on the spin degree of freedom of the electron can be developed. This review focuses primarily on promising candidate materials (such as GaN, GaP and ZnO) in which there is already a technology base and a fairly good understanding of the basic electrical and optical properties. The introduction of Mn into these and other materials under the right conditions is found to produce ferromagnetism near or above room temperature. There are a number of other potential dopant ions that could be employed (such as Fe, Ni, Co, Cr) as suggested by theory [see, for example, Sato and Katayama-Yoshida, Jpn. J. Appl. Phys., Part 2 39, L555 (2000)]. Growth of these ferromagnetic materials by thin film techniques, such as molecular beam epitaxy or pulsed laser deposition, provides excellent control of the dopant concentration and the ability to grow single-phase layers. T...