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.

Electrical conductivity and thermoelectric power measurements of some lithium–titanium ferrites

Abstract: The electrical conductivity and thermoelectric power of some lithium–titanium ferrites with small amounts of manganese and zinc have been studied as a function of temperature in the range of 300–550 K and are reported here. The conductivity variation shows two different regions with a large variation in the activation energies. The possible mechanisms with respect to ionic conduction and electron hopping are discussed with the support of thermoelectric power measurements. Lattice parameters are also calculated from x‐ray diffractograms for confirming the single‐phase nature of the ferrites.

Vibrational, magnetic, and dielectric behavior of La-substituted BiFeO3-PbTiO3

Abstract: Phonons and magnetic and ferroelectric ordering in La-substituted (Bi1−xLax)0.5Pb0.5Fe0.5Ti0.5O3 for samples with 0.0 ≤ x ≤ 0.5 are investigated using Raman, magnetization, and polarization measurements as a function of temperature. The system is tetragonal for pure Bi0.5Pb0.5Fe0.5Ti0.5O3 with a large c/a ratio. The anisotropy is reduced when Bi is partially replaced by La (0 ≤ x ≤ 0.5), and it turns cubic for x ≥ 0.4. All the properties are found to change significantly with changes in the c/a ratio. Evidence of spin-glass-like magnetic ordering at low temperature is found in the case of x = 0.2. A mechanism for the systematic change of magnetic ordering temperature as a function of doping is also discussed. The phonon frequencies and line widths exhibit discontinuous changes across the tetragonal-cubic transition. Large polarization and forbidden Raman scattering in the cubic phase are explained on the basis of symmetry breaking due to the formation of a polar nano region, which leads to relaxor behavior.

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...