Volume 96, Issue 9, 01 November 2004
Index of content:
96(2004); http://dx.doi.org/10.1063/1.1795983View Description Hide Description
Exchange bias and inverted hysteresis loops were observed in the coated particles with a wide distribution of the blocking temperature. The ferromagnetic coupling between the cores and shell is responsible for exchange bias observed below . In the temperature range of , the particles show inverted hysteresis loops, i.e., the negative remanence and coercivity. The most interesting observation is that the particles show an exchange-biased (or shifted) inverted hysteresis loops in between and ; and that the maximum negative remanence appears at where exchange bias disappears. An antiferromagnetic type of interaction between the blocked particles and the superparamagnetic particles is believed to be responsible to the inverted hysteresis loops.
96(2004); http://dx.doi.org/10.1063/1.1801154View Description Hide Description
The microwave absorption dielectric-spectrum technique was used to study the decay kinetics of the free photoelectrons and shallow-trapped electrons in the sulfur-sensitized T-grain crystals prepared under different sensitization times. It was found that, from the dependence of the kinetic behavior of photoelectrons in the sensitized T-grain emulsions, the optimal sensitization time was . With an increase of the sensitization time, the trap effect of the sulfur sensitization centers varies from the hole trap to shallow electron trap, and to deep electron trap, corresponding to the sulfur sensitization centers in the forms of a monomer, dimmer, and cluster of , respectively. The range of the shallow electron trap depth traps was determined to be .
Analytic, graphical, and geometric solutions for the band edges of one-dimensional photonic band gap materials96(2004); http://dx.doi.org/10.1063/1.1803626View Description Hide Description
The conditions for the band gap edges of one-dimensional photonic band gap(PBG)materials are presented in forms that lead to alternate analytic, graphical, and geometric solutions and interpretations. Heretofore unavailable analytical conditions for the band edges of quarter wave∕half wave and eighth wave∕half wavePBG structures are derived. The graphical solution has the form of an intersection of an invariant (material dependent) figure with a straight (structure dependent) line, a convenient separation not possible with the Kronig-Penney (KP) equation. The geometric solution is represented by the sides and angles of simple triangles. The present formalism should help in visualizing the PBGband gap formation beyond the view offered by the KP equation.
96(2004); http://dx.doi.org/10.1063/1.1755428View Description Hide Description
Structural and magnetic properties have been studied for polycrystalline Low-temperature (∼500 °C) synthesis leaves unreacted starting ZnO and manganese oxides. Contrary to a recent report, no bulk ferromagnetism was observed for single-phase materials synthesized in air at temperatures above 900 °C. Single-phase samples show paramagnetic Curie–Weiss behavior.