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.

Measurement of transition temperatures (simultaneously at DC and microwave frequencies) on high‐Tc superconducting systems

Abstract: A technique for the simultaneous measurement of the dc conductivity and microwave (ac) properties on the same sample is described. The difference in transition temperatures between dc and microwave frequencies (i) at ≈6.2 GHz (J-band), ≈9.2 GHz (X-band), ≈13.5 GHz (P-band), and ≈17.8 GHz (P-band) on YBaCu oxide and (ii) at ≈6.2 GHz on YBaCu oxide thin films and BiPbSrCaCu oxide has been evaluated. From the observations of these simultaneous measurements, the energy dependent variations of these simultaneous measurements, the energy dependent variation of ΔTc (Tc(dc) – Tc(ac)) and the non-zero microwave power loss beyond the superconducting transition temperature are discussed.

Development of a microprocessor-based four probe DC resistivity setup for T/sub c/ measurement of superconducting materials

Abstract: The design of a microprocessor-based resistivity measurement system for high transition temperature (T/sub c/) superconducting materials is described. This design includes interfacing an Intel 8085 microprocessor system with an IBM-compatible personal computer (PC) through RS-232C serial communication. This design is used to measure resistivity for superconducting samples of YBa/sub 2/Cu/sub 3/O/sub 7-x/ and strontium/potassium substituted YBa/sub 2/Cu/sub 3/O/sub 7-x/. A correction method is described for the parameters whose values are changing throughout the measurement period to minimize the measurement errors. >

Photoemission studies on (Sm0.50Ca0.50)MnO3

Abstract: Core and valence level spectra of (Sm0.50Ca0.50)MnO3 are reported. The spectral weight of the valence band has a peak 6 eV below Fermi level. Comparative analysis with the similar class of compounds suggests that width of the valence band is low for this compound. Semiconductor type behaviour of this compound is qualitatively predicted using the features of valence band and core level spectra.

Microwave hall mobility studies on polymer–metal oxide nanocomposites

Abstract: Films of polymer metal oxide composites with poly(methyl methacrylate) and metallic powders (CuO, Ni, and brushed Fe3O4) were prepared with a spin-casting method. Electric transport studies indicated that the compositions surpassed the percolation threshold limit. Alternating current (AC) conductivity studies confirmed a hopping mechanism with power-law behavior in frequency. For the first time, the mobility values of the carriers in these films were measured by the contactless microwave Hall effect technique with a bimodal cavity operating at 14 GHz. In this technique, a circular bimodal cavity is used to measure the change in the transmission coefficient (proportional to the carrier mobility) due to the application of a static magnetic field perpendicular to the microwave electric fields. The mobility measurements indicated a decrease in mobility with increasing quantity of CuO and Ni and showed an increase in the carrier–lattice scattering, whereas the mobility increased with increasing Fe3O4 due to the negative magneto resistance. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

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...