Solid State Physics Laboratory

About: Solid State Physics Laboratory is a facility organization based out in Delhi, India. It is known for research contribution in the topics: Quantum dot & Dielectric. The organization has 1754 authors who have published 2597 publications receiving 50601 citations.

Defect structure of the solid solutions Ba1-xGdxF2+x.

Abstract: In this paper we present the results of a series of combined experiments on solid solutions ${\mathrm{Ba}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Gd}}_{\mathrm{x}}$${\mathrm{F}}_{2+\mathrm{x}}$ employing the following techniques: (a) ionic thermocurrents (ITC's); (b) dielectric capacitance and loss measurements at 1000 Hz; and (c) EPR. In line with earlier results on solid solutions ${\mathrm{Sr}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Gd}}_{\mathrm{x}}$${\mathrm{F}}_{2+\mathrm{x}}$ we find a discrepancy between the numbers of dipoles as observed with the dielectric relaxation techniques [(a) and (b)] and the spectroscopic EPR method, respectively. It appears that this discrepancy is caused by the fact that in dielectric experiments the dipoles are detected through their dynamical properties, whereas the EPR results provide a static picture. With ITC we only observe those dipoles which are isolated from the remaining defect system. The most important feature of our EPR data is that trigonal ${\mathrm{Gd}}^{3+}$ ions are by far the dominant defects present in ${\mathrm{Ba}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Gd}}_{\mathrm{x}}$${\mathrm{F}}_{2+\mathrm{x}}$ even for 0x0.05. This has important consequences for the conductivity processes in heavily doped materials. The defect properties of the system ${\mathrm{Ba}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Gd}}_{\mathrm{x}}$${\mathrm{F}}_{2+\mathrm{x}}$ deviate from those observed for cubic solid solutions consisting of ${\mathrm{CaF}}_{2}$ and rare-earth fluorides, which show extensive preferential clustering.

EPR study of molecular ordering in liquid crystal: NOBA†

Abstract: The molecular ordering in the nematic and smectic-C phases of the liquid crystal p-n-nonyloxy benzoic acid (NOBA) is investigated. The phase transition from isotropic to nematic phase is of first order. In the nematic phase over a wide range of temperatures the order parameter remained constant. In the low temperature nematic phase a possible mechanism namely polymerisation involving hydrogen bonds is suggested. The apparent fall in the order parameter at nematic to smectic-C tramition is attributed to the tilt angle in the smectic-C phase. Die Molekularordnungen in der nematischen und smektischen C-Phase von flussigen p-n- nonyloxy-benzoe-Saure(NOBA)-Kristallen wird untersucht. Der Phasenubergang von der isotropen zur nematischen Phase ist von erster Ordnung. In der nematischen Phase bleibt der Ordnungsparameter uber einen weiten Temperaturbereich konstant. Fur die nematische Tieftemperaturphase wird ein moglicher Mechanismus namlich Polymerisation unter Beteiligung von Wasserstoffbindungen vorgeschlagen. Der auftretende Abfall des Ordnungsparameters beim Ubergang nematischer zur smektischen C-Phase wird dem Kippwinkel in der smektischen C-Phase zugeschrieben.