Department of Physics
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Item Magnetic phase transitions in Fe{sub 80-x}Ni{sub x}Cr{sub 20} (14 {<=} x {<=} 30) alloy studied by using {sup 57}Fe Moessbauer spectroscopy(ETDE Web, 1999-11) Bandyopadhyay, DebashisThis paper reports {sup 57}Fe Moessbauer spectroscopic studies of the polycrystalline samples of the substitutionally disordered, isostructural (fcc), ternary alloy system Fe{sub 80-x}Ni{sub x}Cr{sub 20} for x = 30, 26, 19 and 14 in the temperature range of 10-295 K. The data have been analyzed in terms of the magnetic phase transitions occurring in these alloys by examining the temperature dependence of the various Moessbauer parameters like line-width, center shift, resonance area, distribution of hyperfine field, P(H), and the average hyperfine field . An estimate of the magnetic transition temperature T{sub C} is made for the alloys with x = 30 and 26 and these results are compared with those previously obtained by magnetic measurements and neutron diffraction experiments. The data for the second order Doppler shift have been analyzed to estimate the Debye temperature {theta}D for alloys with x = 30 and 26.Item A study of the effect of annealing temperatures and time periods on the hyperfine field distributions of Fe79B16Si5 metallic glass near and below the crystallization temperature was carried out using 57Fe Mössbauer spectroscopy. The effect of crystallization during annealing as a function of annealing time on the average hyperfine magnetic field, , and the relative change of the probability of hyperfine fields, P(H), with respect to that of the as-received sample are also discussed.(Springer, 1999-11) Bandyopadhyay, DebashisThis paper reports 57Fe Mössbauer spectroscopic studies of the polycrystalline samples of the substitutionally disordered, isostructural (fcc), ternary alloy system Fe80-xNixCr20 for x = 30, 26, 19 and 14 in the temperature range of 10–295 K. The data have been analyzed in terms of the magnetic phase transitions occurring in these alloys by examining the temperature dependence of the various Mössbauer parameters like line‐width, center shift, resonance area, distribution of hyperfine field, P(H), and the average hyperfine field 〈H〉. An estimate of the magnetic transition temperature T C is made for the alloys with x = 30 and 26 and these results are compared with those previously obtained by magnetic measurements and neutron diffraction experiments. The data for the second order Doppler shift have been analyzed to estimate the Debye temperature ΘD for alloys with x = 30 and 26.Item A study of the effect of annealing on the hyperfine field distributions in Fe79B16Si5 metallic glass(Elsevier, 1999-12) Bandyopadhyay, DebashisA study of the effect of annealing temperatures and time periods on the hyperfine field distributions of Fe79B16Si5 metallic glass near and below the crystallization temperature was carried out using 57Fe Mössbauer spectroscopy. The effect of crystallization during annealing as a function of annealing time on the average hyperfine magnetic field, , and the relative change of the probability of hyperfine fields, P(H), with respect to that of the as-received sample are also discussed.Item Purpose-led Publishing logo. Study of hyperfine-field distributions and the lattice dynamics of Fe50Ni30Cr20 alloy by using 57Fe Mössbauer spectroscopy(IOP, 1999) Bandyopadhyay, DebashisThis paper reports a 57Fe Mössbauer spectroscopic study of a polycrystalline sample of the substitutionally disordered, isostructural (fcc), ternary alloy Fe50Ni30Cr20 over the temperature range 10 to 295 K. The data have been analysed in terms of the magnetic phase transitions occurring in the alloy by examining the temperature dependence of the Mössbauer parameters. The Curie temperature has been determined by fitting the average hyperfine-field values obtained at different temperatures. In order to achieve a detailed understanding of the nature of the hyperfine-field distribution corresponding to the Mössbauer spectra of this alloy, the curves representing the probabilities of the hyperfine-field distributions versus the hyperfine field have been refitted by using two independent Gaussians. On the basis of these fits, the local magnetic ordering of this alloy at low temperature has been described. The data on the second-order Doppler shift have been analysed in order to obtain an estimate of the Debye temperature, ΘD, and a description of the lattice dynamics.Item Mössbauer spectroscopic study of the effect of annealing on the hyperfine field distributions in Fe78B13Si9 metallic glass(Elsevier, 1999-02) Bandyopadhyay, DebashisA study of the effect of annealing temperatures and time periods on the hyperfine field distributions of Fe78B13Si9 metallic glass near and below the crystallization temperatures was made by using 57Fe Mössbauer spectroscopy. The effect of crystallization during annealing as a function of annealing time on the average hyperfine field () and the relative change of the probability of hyperfine fields, P(H), with respect to that of as-received samples has also been discussed.Item The Ti-Cr-C (titanium-chromium-carbon) system(Springer, 1999-05) Bandyopadhyay, DebashisThe assessed phase diagram of Ti-C system in Fig. 1 is taken from [98Oka]. Other recent assessments of this were done by [95Alb],[96Jon], and [96Sei]. The system consists of two terminal solids αTi and βTi and a refractory monocarbide TiC. Other phases present are liquid (L) and graphite (C). Two eutectic and one peritectoid reactions appear in this system at 1646, 2776, and 920 C, respectively. Crystal structure data shownItem Mossbauer spectroscopic study of heat-treated and control-cooled Fe3Al alloys(Springer, 1998-01) Bandyopadhyay, DebashisThe Fe–Al system forms a model object of transition metal-sp element system. Fe–Al alloys containing 21–31 at% Al are known to exhibit several attractive physical properties which render them candidate materials for structural and magnetic applications. These magnetic and physical properties can be varied by altering the composition and the processing routes. Keeping this in mind, Mossbauer spectra of five Fe–24 at% Al and Fe–25 at% Al alloy samples processed via different routes have been studied. The analysis of the Mossbauer parameters, distribution of hyperfine magnetic fields, P(H) and H-values were used to identify various Fe-atom configurations (nearest neighbour or next nearest neighbour) associated with the phases formed by different processing routes. The results obtained from the present study indicate that the average hyperfine field 〈H〉 depends on the average rate of cooling followed during the precipitation of these phases.Item The Ti-Mo-C (Titanium-Molybdenum-Carbon) System(Springer, 1999-05) Bandyopadhyay, DebashisThe assessed phase diagram of the Ti-C system shown in Fig. 1 is taken from [98Oka]. The system consists of two terminal solids, αTi, βTi, and a refractory monocarbide TiC. Other phases are liquid (L) and graphite (C). Two eutectic reactions and one peritectoid reaction appear in this system at 1650, 2776, and 920 C, respectively. Crystal structure data of the Ti-C system shown in Table 1 are taken from [Massalski2].Item The Ti-WC (titanium-tungsten-carbon) system(Springer, 1999) Bandyopadhyay, DebashisThe assessed phase diagram of Ti-C system shown in Fig. 1 is drawn on the basis of information provided by [96Sei] and [98Oka]. Other recent work on this system has been done by [95Alb] and [96Jon1]. The system consists of two terminal solid solutions (αTi) and (βTi) and a refractory monocarbide (TiC). Other phases are liquid (L) and graphite (C). Two eutectic and one peritectoid reactions appear in this system at 1646, 2776, and 920 C, respectively.