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Electrical resistivity of RNi4Al and RNi4Cu

Toliński T., Ivanov V., Kowalczyk A.

Materials Science Poland

2006

Vol. 24, No. 3

789--793

A comparative studies of the temperature dependence of resistivity for RNi4X (X = Al, Cu; R = Y or rare earth) compounds are presented. These results are also compared to the previously studied RNi4B. The ordering temperatures are well identified on the ?(T) curves. The residual resistivity ?0 of RNi4Al is several times higher than for RNi4Cu and RNi4B. The YNi4X compounds are included in these studies as the nonmagnetic isostructural reference materials. The phonon contribution has been determined for both Y-based compounds employing the Bloch-Grüneisen formula. The CeNi4X compounds show a shallow minimum in ?(T) at low temperatures (about 15 K). This anomaly has been ascribed to a Kondo impurity - like behavior. For the other rare earths, the ?(T) dependences below TC have been analyzed assuming the scattering on magnons as the predominant mechanism.

Electrical substitution cryogenic radiometer based spectral responsivity scale between 250–2500 nm wavelengths

Bazkir O., Samedov F.

Optica Applicata

2004

Vol. 34, nr 3

427-438

This paper presents the spectral responsivity scale between 250–2500 nm developed by the National Metrology Institute of Turkey (UME). For that purpose silicon photodiode based trap detector and electrically calibrated pyroelectric radiometer (ECPR) that were calibrated against primary level absolute electrical substitution cryogenic radiometer (ESCR) were used as transfer standards. Using highly collimated and stabilized (10–5) lasers, absolute optical powers and absolute responsivity of trap detector were measured with an uncertainty of the order of 10–4. In visible (VIS) region responsivity scale was set by means of the models for the reflectance and internal quantum efficiency. In the ultraviolet (UV) and near-infrared (NIR) regions spectrally flat (0.1%) ECPR was used.