Suram Singh

Synthesis and characterization of K2NiF4-type phases Ln0.5Sr1.5Mn0.5Fe0.5O4 (Ln = La, Nd, Gd, and Dy)

A systematic investigation of layered perovskite oxides with general formula Ln0.5Sr1.5Mn0.5Fe0.5O4 (Ln = La, Nd, Gd, and Dy) has been undertaken mainly to understand their structural, magnetic, as well as electrical behavior. The materials were prepared by the ceramic method. X-ray data have been analyzed by using program Checkcell and the variations of various parameters are explained. It has been concluded that not only A-site cation radius, , but also the size variance factor (σ2) influence electrical and magnetic properties. A systematic study of electrical resistivity of all the four materials was undertaken as a function of temperature to understand the conduction mechanism. On analyzing the electrical resistivity data, it has been concluded that variable range hopping model is found to fit well. The magnetic studies suggest that the phases are antiferromagnetic and this behavior could arise from Mn4+–O–Mn4+, and Fe3+–O–Fe3+ superexchange interaction.

THEORETICAL INVESTIGATION OF POSITIVE PARITY BAND STRUCTURE OF Y AND Nb ISOTOPES

The positive parity band structure of odd mass neutron-rich 97–103Y and 99–105Nb nuclei has been studied using microscopic technique known as the projected shell model (PSM) with the deformed single-particle states generated by the standard Nilsson potential. The nuclear structure properties like yrast spectra, energy splitting, moment of inertia, rotational frequencies and reduced transition probabilities B(M1) and B(E2) have been calculated and their comparison with the available experimental data has been made. A shape evolution has also been predicted in these isotopes as one moves from 97Y to 99Y and 99Nb to 101Nb. The PSM calculations also demonstrate the multi-quasiparticle structure in these nuclei.

A fast and area-efficiency BWC array D/A and A/D conversion scheme

A modification to D/A and A/D converters of the charge redistribution type is suggested. It reduces the silicon area requirement by a factor of two or more (up to 6.5 for 8-bit converters) and increases the speed by a similar factor, while retaining compatibility to presently used MOS fabrication processes. The scheme is sufficiently insensitive to undercuts and parasitics. Under the scheme, some of the LSB (least-significant bit) side branch capacitors are realized as a series combination of unit capacitors and the higher-bit capacitances are adjusted to make them binary-weighted to the LSB capacitances. Simulation results and an implemented binary-weighted capacitor (BWC) scheme are shown. >

Theoretical study of neutron-rich 107,109,111,113Rh isotopes

A theoretical study of the structure of some odd mass Rh nuclei in the A ~ 100 mass region is carried out by using the angular momentum projection technique implemented in the projected shell model (PSM). The influence of the high-j orbitals (h11/2 for neutrons and g9/2 for protons) on the structure of 107–113Rh isotopes is investigated in the present case by assuming an axial symmetry in the deformed basis. For these isotopes, the structure of multi-quasi-particle qp bands is studied along the yrast line in detail. Further, the phenomenon of back-bending is also studied theoretically and is found to be in agreement with the experimental data. The reduced transition probabilities, i.e., B(E2) and B(M1) for the yrast band are also obtained from the PSM wave functions for the first time, thereby providing an opportunity for the experimentalists to work for this data.

Structure and magnetic properties of nano-sized perovskite oxide La0.5Sr0.5Ti0.5Fe0.4Cr0.1O3 synthesized by the citrate precursor method

A new nano-sized perovskite oxide La0.5Sr0.5Ti0.5Fe0.4Cr0.1O3 has been prepared according to the citrate precursor method at two different temperatures. Rietveld profile analysis shows that the phase crystallizes with the orthorhombic unit cell in the space group Pbnm. The size reduction due to the decrease in calcination temperature leads to an increase in lattice parameters and an expansion of the cell volume. The average grain size obtained from the TEM measurement is found to be larger than the observed crystal size obtained from XRD. The magnetic studies suggest that the anti-ferromagnetic interactions are dominant because of Fe3+–O–Fe3+ and Cr3+–O–Cr3+ exchange interactions.Graphical Abstract

MICROSCOPIC STUDY OF NEGATIVE PARITY YRAST STATES IN NEUTRON-DEFICIENT 119–127Ba ISOTOPES

The negative parity yrast bands of neutron-deficient 119–127Ba nuclei are studied by using the Projected Shell Model approach. Energy levels, transition energies and B(M1)/B(E2) ratios are calculated and compared with the available experimental data. The calculations reproduce the band head spins of negative parity yrast bands and indicate the multi-quasiparticle structure for these bands.

Theoretical investigation of nuclear structure properties of 144Gd, 146Dy and 148Er isotones

Some N=80 isotones (144Gd, 146Dy and 148Er) have been studied by using the HFB framework and the nuclear structure properties like yrast spectra, subshell occupation numbers and quadrupole moments have been obtained. Intrinsic quadrupole moments obtained from HFB calculations show a gradual increase as one moves from 144Gd to 148Er indicating, thereby, an increase in deformation, which is in agreement with the experimental results. From the results of subshell occupation numbers, it is clear that subshells 3s1/2, 2d3/2, 2d5/2, 1g7/2 and 1h11/2 of protons are contributing towards the development of deformation as one moves from 144Gd to 148Er.

Study of odd mass 115−125Sb isotopes with the projected shell model calculations

The projected shell model (PSM) with the deformed single-particle states, generated by the standard Nilsson potential, is applied to study the negative-parity high spin states of 115–125Sb nuclei. The nuclear structure quantities like band structure and back-bending in moment of inertia have been calculated with PSM method and are compared with the available experimental data. In addition, the reduced transition probabilities, i.e., B(E2) and B(M1), are also obtained for the yrast band of these isotopes for the first time by using PSM wave function. A multi-quasiparticle structure has been predicted for 115–125Sb isotopes by the present PSM calculations.

Synthesis, structure, and magnetic properties of the perovskite La0.3Sm0.2Sr0.5Ti0.5Fe0.5O3

Perovskite oxide La0.3Sm0.2Sr0.5Ti0.5Fe0.5O3 has been synthesized by a citrate-gel precursor method. The Rietveld analysis of the XRD data showed that the sample crystallizes with a orthorhombic structure in the space group Pbnm. Magnetic properties suggest that antiferromagnetic interactions are dominant due to Fe3+–O–Fe3+ units.Graphical abstract

Study of yrast structures in 55,57Cr

The characteristic nuclear structure properties of yrast bands of 55,57Cr have been investigated by using two body effective interactions incorporated in phenomenological axial framework. In order to check the validity of the chosen framework as well as chosen valence space, the calculated results are compared with the available experimental data and a good agreement has been found from the comparison. The back-bending in moment of inertia has also been studied and attributed to the alignment of odd g9/2 neutron along the rotation axis.