NOPR Collection:

Magnetic properties of Cd and Al substituted cobalt ferrite

2013-12-10T16:38:17Z

Title: Magnetic properties of Cd and Al substituted cobalt ferrite Authors: Shitre, A R; Devatwal, U N; Birajdar, D S; Jadhav, K M Abstract: The crystal structure and magnetic properties of simultaneously substituted cadmium and aluminium spinel series Co_1-xCd_xFe_2-xAl_xO₄ with x=0.0, 0.1, 0.2, 0.3, 0.4 and 0.5, are studied by X-ray diffraction and saturation magnetization measurements. The single phase fcc spinel structure of all the samples was confirmed by X-ray diffraction. X-ray analysis showed that the latticc parameter 'a', increases with increasing x. The apparent density and X-ray density exhibit similar behaviour. The Bragg peaks of XRD patterns were used to determine the possible cation distribution among the tetrahedral (A) and octahedral rB] sites. X-ray intensity calculations indicate that Cd²⁺ and Al³⁺ ions occupy tetrahedral (A) and octahedral [B] sites respectively, while Fe³⁺ ions occupy both tetrahedral (A) and octahedral [B] sites. The saturation magnetization ‘σ_s’and magneton number 'n_B' (the saturation magnetization per formula unit) measured at 300 K using high field hysteresis loop technique decrease with increasing x, suggesting decrease in ferrimagneric behaviour. Neel's two sublattice model is applicable up to x≤ 0.2 while Y-K three sublattice model is applicable for x≥ 0.2. The cation distribution obtained from magnetization data is in good agreement with the cation distribution estimated from X-ray intensity calculations. The Neel temperature T_N deduced from a.c. susceptibility data decreases with x, suggesting a decrease in ferrimagnetic behaviour. Page(s): 464-468

Life-time measurements of doped zinc sulphide under nitrogen laser excitation

2013-12-03T16:39:48Z

Title: Life-time measurements of doped zinc sulphide under nitrogen laser excitation Authors: Bhatti, H S; Verma, N K; Kumar, Sunil Abstract: Excited state lifetime measurements have been carried out for zinc sulphide doped with copper and silver activators having doping concentrations 0.03 to 0.40% by weight using nitrogen laser as the excitation source having pulse-width (10 ns), energy per pulse (2 mJ), and pulse repetition rate (50 Hz). The effect of dopant-concentration has been studied at room temperature as well as at liquid nitrogen temperature; the lifetimes are found to remain more or less constant except at room temperature. The decrease in temperature of the sample is found to make its decay faster. Page(s): 461-463

Chemical and electronic spectral studies of ullmannite (Ni₄Sb₄S₄)

2013-12-03T16:39:43Z

Title: Chemical and electronic spectral studies of ullmannite (Ni₄Sb₄S₄) Authors: Reddy, S N; Ravikumar, R V S S N; Reddy, B J; Reddy, Y P Abstract: The streak grayish black coloured and almost opaque mineral ullmannite belonging to France received from Musee De Mineralogie, Ecole Natle, Supre Des Mines, Paris, France, has been investigated by atomic absorption spectroscopy (AAS) and optical absorption spectroscopy. The AAS analysis shows that the mineral contains the transition elements nickel (1. 14%), iron (0.29%), cobalt (0.073%), copper (0.013%), and manganese (0.003 1 %). The bands observed at 25967, 24993, 21546, 14966, 12252 and 861 8 cm^-1 in the optical absorption spectrum recorded at room temperature are assigned to different transitions of Ni(lI) ion. The following crystal field parameters are evaluated: Dq = 860 cm^-1, B = 840 cm^-1, and C= 3350 cm^-1, respectively. These values confirm the octahedral symmetry for Ni(II) in the mineral ullmannite. Page(s): 459-460

Conductivity and DSC studies of poly(ethylene glycol) and its salt complexes

2013-12-03T16:39:28Z

Title: Conductivity and DSC studies of poly(ethylene glycol) and its salt complexes Authors: Murugendrappa, M V; Khasim, Syed; Prasad, M V N Ambika Abstract: The temperature response of conductivity of poly(ethylene glycol) (PEG) and its salt complexes like KCI, KBr and KI has been studied in the temperature range 299 to 331 K. Doping of PEG with KCI and KBr increased the conductivity by about 2.5 times for KCI and about 6.25 times for KBr, while doping with KI reduced the conductivity to about 0.05 times its pure component value. This may be due to the presence of dissolved salt in the solid, or alternatively may be due to the changes in the structure of PEG induced by the presence of salt. DSC studies on the samples were carried out wherein a beautiful peak was observed near the melting point. Analysis of DSC results confirms that the reaction is endothermic and the peak shifts towards higher value for different salts as compared to pure PEG. Page(s): 456-458

NOPR Collection:

Magnetic properties of Cd and Al substituted cobalt ferrite

Life-time measurements of doped zinc sulphide under nitrogen laser excitation

Chemical and electronic spectral studies of ullmannite (Ni4Sb4S4)

Conductivity and DSC studies of poly(ethylene glycol) and its salt complexes

Chemical and electronic spectral studies of ullmannite (Ni₄Sb₄S₄)