Flux dependent 1.5 MeV self-ion beam induced sputtering from Gold nanostructured thin films

We discuss four important aspects of 1.5 MeV Au2+ ion-induced flux dependent sputtering from gold nanostrcutures (of an average size 7.6 nm and height 6.9 nm) that are deposited on silicon substrates: (a) Au sputtering yield at the ion flux of 6.3x10^12 ions cm-2 s-1 is found to be 312 atoms/ion which is about five times the sputtering yield reported earlier under identical irradiation conditions at a lower beam flux of 10^9 ions cm-2 s-1, (b) the sputtered yield increases with increasing flux at lower fluence and reduces at higher fluence (1.0x10^15 ions cm-2) for nanostructured thin films while the sputtering yield increases with increasing flux and fluence for thick films (27.5 nm Au deposited on Si) (c) Size distribution of sputtered particles has been found to vary with the incident beam flux showing a bimodal distribution at higher flux and (d) the decay exponent obtained from the size distributions of sputtered particles showed an inverse power law dependence ranging from 1.5 to 2.5 as a function of incident beam flux. The exponent values have been compared with existing theoretical models to understand the underlying mechanism. The role of wafer temperature associated with the beam flux has been invoked for a qualitative understanding of the sputtering results in both the nanostructured thin films and thick films.Comment: 25 pages, 5 figures, 1 table To be Appeared in J. Phys. D: Appl. Phy

Effect of strain on the transport properties of the manganite systems

The effect of strain on the resistivity and thermopower of ferromagnetic manganites has been examined based on the model that incorporates the electron-lattice interaction through the Jahn-Teller effect and an effective hopping determined by nearest neighbour spin-spin correlation of t2g electrons. The metal insulator transition temperature associated with resistivity decreases with increase in strain. In the presence of large strain the system remains in the semiconducting state. Thermopower (S) is positive and increasing function of strain and it exhibits a maximum with temperature. The temperature where maximum of S appears, shifts towards higher (lower) value with in the presence of magnetic field (strain). A large magneto-thermopower that depends on strain is obtained around metal-insulator transition.Comment: 11pages, 4 figure

Magnetic Field and Displacement sensor based on Giant Magneto-impedance effect

A two-core transducer assembly using a Fe73.5Nb3Cu1Si13.5B9 ribbon to detect a change of magnetic field is proposed and tested for displacement (linear and angular) and current sensor. Two identical inductors, with the ribbon as core, are a part of two series resonance network, and are in high impedance state when excited by a small a.c field of 1MHz in absence of d.c biasing field (Hdc). When the magnetic state of one inductor is altered by biasing field, produced by a bar magnet or current carrying coil, an ac signal proportional to Hdc is generated by transducer. The results for the sensitivity and linearity with displacement (linear and angular) of a magnet and with field from the current carrying coil are presented for two particular configurations of the transducer. High sensitivities of voltage response as much as 12micro-volt/micro-meter and 3mV/degree have been obtained for the transducer as a linear and angular displacement sensor respectively in the transverse configuration of exciting a.c and biasing d.c fields.Comment: 16 pages,7 figure