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

Microwave power loss and XPS measurements on high Tc NdBaCuOxide superconducting system

Structure analysis on the Ba3Mg(Ta1−xNbx)2O9 ceramics: Coexistence of order and disorder

The reorientation activation energies of five methanol + ketone systems were determined from the study of the variation of dielectric permittivity with temperature between 303 to 333 K at X band frequency. The results of the activation parameters are interpreted in terms of the rotation of the molecules about the C–O–H hydrogen bond, using a previously reported conformation obtained from semi-empirical and ab initio calculations as the basic conformer. The ketones studied are acetone, 2 butanone, 3 pentanone, cyclohexanone and acetophenone.

Effect of steric hindrance of ketones in the dielectric relaxation of methanol+ketone systems

Dielectric dispersion and Raman studies are carried out on the solid solution series (BaxPb1−x)(Yb0.5Nb0.5)O3 from x = 0.0 to 0.3. The x-ray diffraction analysis indicates that with the substitution of Ba2+, the intensity of the peaks corresponding to antiparallel displacement of Pb2+ decreases and the structure becomes cubic. The low frequency dielectric dispersion studies indicate that the series undergoes a transition from an antiferroelectric to a relaxor ferroelectric with variation of x. Raman spectra of the compositions indicate the presence of a greater number of modes for the compounds with cubic structure (). A new mode at 420 cm−1 is observed for the compounds with Ba2+ substitution. The intensity of this mode increases monotonically with increase in Ba2+ substitution and this has been attributed to the commencement of local distortion. This could be responsible for the appearance and increase in the diffuseness around Tmax, the temperature corresponding to .

http://iopscience.iop.org/article/10.1088/0953-8984/17/2/011/pdf

Dielectric and Raman studies of (BaxPb1−x)(Yb0.5Nb0.5)O3

Measurement of Hall mobility in semiconductor samples using bimodal cavity method gives distinct advantages due to noncontact nature as well as the provision to measure anisotropic mobility. But the measurement approaches followed till now have a disadvantage of having high error values primarily due to the problem in evaluating the calibration constant of the whole experimental arrangement. This article brings out a new approach that removes such disadvantage and presents the calibration constant with 1% accuracy. The overall error in the carrier mobility values is within 5%.

V. R. K. Murthy

Papers

Microwave power loss and XPS measurements on high Tc NdBaCuOxide superconducting system

Structure analysis on the Ba3Mg(Ta1−xNbx)2O9 ceramics: Coexistence of order and disorder

Effect of steric hindrance of ketones in the dielectric relaxation of methanol+ketone systems

Dielectric and Raman studies of (BaxPb1−x)(Yb0.5Nb0.5)O3

New approach for measuring the microwave Hall mobility of semiconductors