Observation of giant T<SUB>c</SUB> depression effect in Y<SUB>1</SUB>Ba<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-d</SUB> doped simultaneously with Zn and Fe

The case of simultaneous doping of Fe and Zn in Y1Ba2Cu3O7-d is examined in the context of the issue of Tc depression by magnetic impurities in the high Tc superconductors. It is observed that codoping of Fe (magnetic) and Zn (diamagnetic) impurities in Y1Ba2Cu3O7-d leads to giant Tc depression, with an almost complete loss of superconductivity for the total dopant concentration above a certain value; while separate doping of Fe or Zn at the same total concentration yield well defined superconducting transitions; though with reduced Tc as compared to the pure 92 K material

Ion-beam mixing at the Fe/SiO<SUB>2</SUB> interface: a conversion-electron Mossbauer spectroscopy and x-ray-diffraction study

The effect of ion-beam-induced atomic mixing and subsequent thermal transformations at the Fe:SiO2 (single crystal) interface have been investigated by means of conversion-electron Mossbauer spectroscopy and small-angle x-ray-diffraction measurements. The ion-beam-mixed sample in the as-mixed state shows the presence of the Fe7SiO10 phase along with magnetic Fe-Si-O complexes. The mixed state undergoes structural modifications upon annealing at 450 &#176;C for several hours leading to an increase in Fe3+-to-Fe2+ ratio. The as-deposited sandwich structure upon annealing at 450 &#176;C leads to the formation of metal island structures

Conversion electron Mossbauer spectroscopic study of ion-beam mixing at Fe-Mo interface

Ion beam induced atomic mixing at Fe-MO interface has been studied by using the technique of conversion electron mossbauer spectroscopy (CEMS). Use has been made of a thin (~50 &#197;) layer of Fe57 isotope (enriched to 95.4%) at the interface to obtain the mossbauer information selectively from this region. A noninterface sensitive measurement has also been performed to reveal the magnetic hyperfine interactions in the entire region of the iron overlayer. It is shown that a deposition induced reaction between the molybdenum substrate (having a thin coating of native oxide) and the Fe57 layer renders a graded nature to the interface, which is transformed upon ion bombardment (100 keV Kr+, dose ~1016 ions/cm2) into a disordered alloy. The dominant nonmagnetic component corresponding to the interface of the ion beam mixed sample happens to be a quadrupole doublet, which represents the presence of Fe57 atoms in Fe2+ charge state. The appearance of this contribution is attributed to formation of an oxygen coordinated ternary compound in the interface layer during ion bombardment. On the basis of the comparison of the results of the interface-sensitive and non-interface-sensitive studies it is established that the inclusion of oxygen in the ion mixed sample is mainly confined to near interface region and that the region of the overlayer contains a metastable alloy of the binary Fe-Mo system. The influence of thermal annealing at various temperatures between 200&#176;C and 500&#176;C on the ion beam mixed state has also been studied by monitoring the changes in the hyperfine interaction parameters. It is shown that the oxygen-incorporated regions of the disordered alloy retain the nonmagnetic Fe2+ charge state subsequent to annealing at 500&#176;C, while other regions lead to precipitation of &#945; Fe and Fe2Mo phases

Pulsed-laser-induced reactive quenching at liquid-solid interface: aqueous oxidation of iron

High-power pulsed-laser-induced reactive quenching at liquid-solid interface is used for the first time to synthesize a metastable form of iron oxide. The oxide phase is characterized by using the techniques of conversion-electron Mossbauer spectroscopy, Rutherford backscattering spectrometry, x-ray diffraction, and x-ray photoelectron spectroscopy

Ion beam mixing at Fe:Al<SUB>2</SUB>O<SUB>3</SUB> interface: a conversion electron Mossbauer spectroscopy study

The effect of ion beam induced atomic mixing and subsequent thermal transformations at the Fe:Al2O3 interface have been investigated by means of conversion electron Mossbauer spectroscopy [CEMS]. It is shown that the asdeposited and ion beam mixed samples exhibit distinctly different features. In particular, the ion beam mixed sample in as-mixed state shows the presence of FeAl2O4 along with non-stoichiometric FeO. Upon annealing at 600&#176;C it shows precipitation of &#945;-Fe with reduced contribution of FeAl2O4. The study of dose dependence of ion beam mixing has also revealed interesting features regarding the ion beam induced interface reactions