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 …

I and i

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.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

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.

Ferromagnetic materials

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

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

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...

/pdf/wide-band-gap-ferromagnetic-semiconductors-and-oxides-48l1gtt253.pdf

Wide band gap ferromagnetic semiconductors and oxides

This paper presents the investigation on the propagation of microwaves through the square lattice structure constructed by two different materials, glass (ϵ r = 5.5) and poly vinyl chloride (PVC) (ϵ r = 2.38). We report the transmission spectra of these structures that were recorded between 7 and 20 GHz. It is observed that the glass structure of lattice constant 1.4 cm gave a band gap centered around 17 GHz with a gap width of 3.5 GHz and attenuation of 30 dB. With PVC rods, the spectra were recorded for two different lattice constants 1.4 cm and 1.1 cm. The structure of 1.4 cm shows a band gap centered at 16.8 GHz with a gap width of 1.48 GHz where as the structure of 1.1 cm lattice constant shows a band gap centered at 11.17 GHz with a gap width of 2.67 GHz. The attenuation in both cases is around 25 dB. The analysis shows that the gap width is low for structures made of PVC rods when compared to structure made of glass as expected because of the low dielectric constant of PVC. It is also observed that...

Microwave Propagation in a Square Lattice Using Different Dielectric Materials for Device Applications

A Nuclear Double Resonance Spectrograph has been designed and constructed with emphasis on quadrupolar nuclei of half-integral spins. The use of a data acquisition and processing system featuring the A/D converter, signal averager with built in fast Fourier transformation hardware greatly improves the S/N ratio. The spectrograph has been used to detect certain organochlorine, carbamate and symmetrical triazine pesticides. Concentration levels that can be detected range from 15 to 100 micrograms per liter. Since the measurements are done below ice temperatures, heat-labile compounds can be detected without conversion to more suitable derivatives as in gas chromatography. Fats and oils in sample extracts do not interfere with the measurements. Further improvement in sensitivity is possible by using liquid nitrogen-cooled, ferrite-cored electromagnet, by increasing the polarizing field and by reducing receiver recovery time. In addition to analysis of pesticides, the Nuclear Double Resonance technique can be used to study the electronic structure of molecules.

/pdf/development-of-a-new-technique-for-the-analysis-of-1ktuu1hovj.pdf

Development of a New Technique for the Analysis of Pesticides in Water

Effect of thickness and length of the sample on the dielectric constant (ε|) and loss (ε∥) measurements in the microwave cavity perturbation technique

Room temperature measurements of the 0.5-2.0 eV optical reflectance of carefully prepared pure stages 3,4,6 and the mixed stages (2,3) and (3,4) graphite-ferric chloride intercalation compound have been performed. The stages show metallic nature with a large contribution from the imaginary part of the dielectric constant. The higher value of the dielectric constant shows the charge transfer from graphite to ferric chloride to be ionic in nature.

V. R. K. Murthy

Papers

Microwave Propagation in a Square Lattice Using Different Dielectric Materials for Device Applications

Development of a New Technique for the Analysis of Pesticides in Water

Effect of thickness and length of the sample on the dielectric constant (ε|) and loss (ε∥) measurements in the microwave cavity perturbation technique

Optical and low frequency conductivity measurements on pure and mixed stages of graphite-ferric chloride intercalation compound

Frequency and temperature dependent dielectric studies of propylene glycol-sulfolane binary mixtures in the microwave frequency region.