• Saibal Basu

      Articles written in Pramana – Journal of Physics

    • Polarized neutron reflectometry at Dhruva reactor

      Surendra Singh Saibal Basu

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      Polarized neutron reflectometry (PNR) is an ideal non-destructive tool for chemical and magnetic characterization of thin films and multilayers. We have installed a position sensitive detector-based polarized neutron reflectometer at Dhruva reactor, Trombay. In this paper we will discuss the results obtained from this instrument for two multilayer samples. The first sample is a (Ni-Mo alloy)/Ti multilayer sample. We have determined the chemical structure of this multilayer by unpolarized neutron reflectometry (NR). The other sample is a Fe/Ge multilayer sample for which we obtained the chemical structure by NR and magnetic moment per Fe atom by PNR.

    • Specular neutron reflectivity and beyond

      Saibal Basu

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      A polarized neutron reflectometer for vertical samples is available at Dhruva reactor guide hall, Trombay. The reflectometer has been designed for horizontal scattering vector. It uses a position-sensitive detector for obtaining the reflectivity pattern. This arrangement allows one to obtain diffuse or off-specular intensity around any specular peak at one go. We have used this instrument for studying the structure of various metal-metal and metal-semiconductor multilayers by specular reflectometry. We have also been successful in understanding interface morphology of several films through diffuse neutron reflectometry (DNR) on this reflectometer. Some of the recent results are presented in this paper to demonstrate the strength of these two techniques.

    • Structure and magnetism of Ni/Ti multilayers on annealing

      Surendra Singh Saibal Basu P Bhatt

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      Neutron reflectometry study has been carried out in unpolarized (NR) and polarized (PNR) mode to understand the structure and magnetic properties of alloy formation at the interfaces of Ni/Ti multilayers on annealing. The PNR data from annealed sample shows a noticeable change with respect to the as-deposited sample. These changes are: a prominent shift of the multilayer Bragg peak to a higher angle and a decrease in the intensity of the Bragg peak. The PNR data from annealed sample revealed the formation of magnetically dead alloy layers at the interfaces. Changes in roughness parameters of the interfaces on annealing were also observed in the PNR data.

    • Scattering length density profile of Ni film under controlled corrosion: A study in neutron reflectometry

      Surendra Singh A K Poswal S K Ghosh Saibal Basu

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      We report the density depth profile of an as-deposited Ni film and density profile for the same film after controlled electrochemical corrosion by chloride ions, measured by unpolarized neutron reflectometry. The neutron reflectometry measurement of the film after corrosion shows density degradation along the thickness of the film. The density profile as a function of depth, maps the growth of pitting and void networks due to corrosion. The profile after corrosion shows an interesting peaking nature.

    • Magnetic depth profiling of Fe/Au multilayer using neutron reflectometry

      Surendra Singh Saibal Basu M Gupta

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      We present unpolarized and polarized neutron reflectometry data on Fe/Au multilayer sample for characterizing the layer structure and magnetic moment density profile. Fe/Au multilayer shows strong spin-dependent scattering at interfaces, making it a prospective GMR material. Fe/Au multilayer with bilayer thickness of 130 Å was grown on Si substrate by RF magnetron sputtering technique. Unpolarized neutron reflectivity measurement yields nuclear scattering length density profile. The magnetic scattering length density profile has been obtained from polarized neutron reflectivity measurements.

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