• S K Ghatak

      Articles written in Bulletin of Materials Science

    • X-ray photoemission study of Fe40Ni40B20 metallic glass

      M L Mukherjee S K Ghatak

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      X-ray photoelectron spectroscopic (XPS) study of the valence band and the core levels of amorphous Fe40Ni40B20 are presented. The oxides which formed at the surface of as-received sample are due to oxidation of iron and boron. For etched samples, the presence of oxide is not discernible, and the chemical environment is predominantly iron-boron-like, while nickel remains unassociated. The valence band has a high density of states at Fermi levels of amorphous Fe40Ni40B20 are presented. The oxides which formed at the surface of B2s and Fe3d states, and metalloids-states respectively.

    • A novel method for sensing rotational speed, linear displacement and current using superconducting BPSCCO magnetic sensor

      T K Dey A Ray S K Ghatak

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      For many decades, magnetic sensors have been of great assistance to mankind in variety of functions that include simple compass based navigational systems to devices that monitor the invisible biological activities. In industries magnetic sensors are in great demand for control and measurement of linear and rotary position sensing etc, because of its non destructive and contact less way of detection. Consequently, newer, smarter and cheaper materials are continuously being explored to suit the varied needs of technological requirements. In the present communication, the characteristics of a magnetic sensor, based on the non linear electromagnetic response of the weak links present in the polycrystalline BPSCCO superconductor are reported. The second harmonic response of sintered superconducting BPSCCO pellet in an alternating magnetic field at 40 kHz and 77 K being a strong linear function of low d.c. magnetic field has been utilized for the development of highly sensitive magnetic field sensors. The noise limited resolution of the sensor is found to be 3.16 × 10–9 T/√ Hz for $H_{a.c.}$ = 16 Oe and frequency 40 kHz. We further demonstrate that such HTSC based magnetic sensors are capable of sensing the rotational speed, small displacement and direct current with good resolution. The experimental methods and results obtained are discussed.

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