We report here the results of magnetic susceptibility of both n- and p-type superconductors, Nd2-xCexCuO4-y (x=0.14, 0.15, 0.16, and 0.18) and NdBa2Cu3-zZnzO7- (z=0 and 0.02) in the temperature range 2 to 300 K and specific heat measurements on p-type superconductors in the temperature range 5T300 K. Crystal-field (CF) analysis of these results has been performed considering J mixing of the lowest eleven multiplets with intermediate-coupled wave functions. The CF analysis of the magnetic susceptibility data is consistent also with the reported inelastic neutron-scattering spectra. The specific heat data have been accounted for by considering Debye, Einstein, and Schottky contributions. © 1995 The American Physical Society.

Sankaranarayanan V

Department Of Physics

Nithya Ravindran

G. Rangarajan

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Physical Review B

We report here structural and directional magnetic susceptibility measurements on single crystals of (Formula presented)(Formula presented)(Formula presented)(Formula presented)(Formula presented) (x=1.0, δ=1, 0.11; x=0.7, δ=0; and x=0.42, δ=0.22). The space group of (Formula presented)(Formula presented)(Formula presented) (Pr-O6) and (Formula presented)(Formula presented)(Formula presented)(Formula presented)(Formula presented) (Pr 0.42-O7) were found to be P4/mmm and that of (Formula presented)(Formula presented)(Formula presented) (Pr-O7) was found to be Pmmm. Also, Pr-O7 was found to be weakly orthorhombic. Directional, magnetic susceptibility measurements in the temperature range 2-300 K revealed a clear peaking in the paramagnetic anisotropy of Pr-O7 around 17 K, and (Formula presented)≳(Formula presented) at all temperatures. However for (Formula presented)(Formula presented)(Formula presented)(Formula presented)(Formula presented) (Pr0.7-O7) and Pr0.42-O7, (Formula presented)≳(Formula presented) at room temperature and (Formula presented)<(Formula presented) for temperatures below 110 and 60 K, respectively. The magnetic susceptibilities have been analyzed in the light of crystalline electric-field effects considering J mixing of all the thirteen multiplets. Intermediate coupled wave functions have also been used in the calculations. Crystal-field interaction is found to be stronger in the case of Pr-O7 compared to Pr-O6 which is also evident from a shorter Pr-O bond length in the case of Pr-O7 than in Pr-O6. A best set of eigenvalues and eigenfunctions has been determined and these are discussed and compared with inelastic neutron scattering data. © 1996 The American Physical Society.

Physical Review B - Condensed Matter and Materials Physics

Structural, magnetic, and crystalline electric-field effects in single crystal

We report the directional magnetic susceptibilities on single crystals of NdBa2Cu3O7-δ. Crystal field (CF) analysis considering orthorhombic symmetry at the Nd3+ site has been performed and a best set of CF parameters have been obtained. The energy levels obtained from the present fit are in good agreement with the inelastic neutron scattering spectra.

Physica B: Condensed Matter

Magnetic susceptibilities and crystalline electric field effects in single crystals of NdBa2Cu3O7-δ

The effect of substitution at the Cu site by the transition elements Fe, Co, Ni, and Zn on the structure and superconducting properties of NdBa2Cu3O7 has been investigated. Compared to the YBa2Cu3-xMxO7+δ (M=Fe, Co, Ni, Zn) system, considerably high solid solubility and drastic Tc suppression is achieved in the Nd 1:2:3 system. The maximum solid solubilities achieved for the dopants are x=1.0 for M=Fe and Co and x=0.8 for M=Ni and Zn. An orthorhombic-to-tetragonal (O→T) transition is observed at x=0.08 for M=Fe, Co similar to the case of the M-doped Y 1:2:3 system. However, a second T→O transition is observed in Nd 1:2:3 at x=0.5 for M=Co and x=0.8 for M=Fe. For the Ni- and Zn-doped phases, an O→T transition is observed at x=0.4 for M=Ni and x=0.5 for M=Zn. The doped phases are superconducting up to x=0.2 (M=Fe, Co, Ni) and x=0.08 (M=Zn). The initial rate of Tc suppression (up to 3.33 at. %) is ∼14 K/at. % for M=Fe, Co, and Ni and ∼28 K/at. % for M=Zn and is much higher than that reported for the Y 1:2:3 system. The Fe- and Zn-doped phases, heated in flowing N2 gas at 800 °C followed by reoxygenation at 450 °C show higher Tc and sharper superconducting transition. Hole doping by Ca substitution (y) at the Nd site in the Zn-doped (x=0.1) semimetallic-semiconducting Nd 1:2:3 phase induces metallicity and superconductivity for y0.1 and a Tc of 32 K is obtained for y=0.2. © 1993 The American Physical Society.

Influence of Cu-site substitution on the structure and superconducting properties of the NdBa2Cu3-xMxO7+δ (M=Fe,Co) and NdBa2Cu3-xMxO7-δ (M=Ni,Zn) systems

The specific heat of superconducting oxide compound, YBa2Cu3O7 -x, is studied using a quasi-adiabatic calorimeter from 4.2 to 60 K. The analysis of the specific heat data below 15 K gives a value of 17 mJ/mole K2 for the electronic heat capacity coefficient. The value of θD(0) is determined to be 397±8 K. The variation of θD with temperature was calculated in the temperature range 4.2 to 60 K. © 1988 Indian Academy of Sciences.

Journal	Physical Review B
ISSN	01631829
Open Access	No