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A. Hanninger

Bio: A. Hanninger is an academic researcher. The author has contributed to research in topics: Heat capacity & Electrical resistivity and conductivity. The author has an hindex of 2, co-authored 2 publications receiving 11 citations.

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TL;DR: In this paper, specific heat measurements of (R, Pr)Ba 2 Cu 3 O 7 (R=Y, Gd) in external fields up to 11 T were presented and analyzed in terms of crystalline electric field (CEF) effects and indicate that in these systems Pr appears to be trivalent rather than tetravalent.

8 citations

Journal ArticleDOI
TL;DR: In this article, the structural chemistry, AC susceptibility, and resistivity measurements of Nd1.85Ce0.15(Cu1-xMx)O4 where Cu/M substitution reduced superconductivity with an initial rate of -4.5 K/mol.
Abstract: The authors report on the structural chemistry, AC susceptibility, and resistivity measurements of Nd1.85Ce0.15(Cu1-xMx)O4 where Cu/M substitution reduces superconductivity with an initial rate of -4.5 K/mol.% Zn while 1% Co or Ni suppresses superconductivity below 4.2 K.

3 citations


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TL;DR: The assumption that nickel is in the 3+ state satisfactorily explains the reduction in hole concentration, a right-shift of the T c versus y curve with x, and the low magnetic moment carried by Ni atoms in the La 2−y Sr y Cu 1−x Ni x O 4+δ system.
Abstract: Magnetization measurements below 50 K on ceramic La 2− y Sr y Cu 1− x Ni x O 4+ δ ( y = 0.1, 0.2; 0⩽ x ⩽0.5) show a progressive diminution of superconducting properties with increasing x . The larger suppressive action of Ni in the y =0.1 system than that for y =0.2 is attributed to the hole-compensating effect of Ni 3+ . The assumption that nickel is in the 3+ state satisfactorily explains: (1) the reduction in hole concentration, (2) a right-shift of the T c versus y curve with x , and (3) the low magnetic moment carried by Ni atoms, in the La 2−y Sr y Cu 1−x Ni x O 4+δ system.

7 citations

Journal ArticleDOI
01 Mar 2016
TL;DR: In this paper, the specific heat and entropy properties of the orthorhombic PrBa2Cu3O6+x compounds in two states of oxygen concentration x, an over doped (OV) with x = 1 and an optimally Doped (OP) withx = 0.95 are reanalyzed below the Neel temperature of the antiferromagnetic ordering of the Pr sublattice T N = 17.5 and 14 K, respectively.
Abstract: The specific heat Cp(T) and entropy S(T) properties of the orthorhombic PrBa2Cu3O6+x compounds in two states of oxygen concentration x, an over doped (OV) with x = 1 and an optimally doped (OP) with x = 0.95 are reanalyzed below the Neel temperature of the antiferromagnetic ordering of the Pr sublattice T N = 17.5 and 14 K, respectively. Two simultaneous anomalies for both states are observed. The first one occurs near the previous spin reorientation phase transition temperature T 2 ~ 11.5 and ~ 9-10 K, respectively whereas the second one remains close to the so called low-critical temperature Tcr ~ 4-5 K for the OV state as it has been reported before for the OP state. By fitting the C p(T)/T data to A{T 2}-3/2 + γ + C{T 2}1 + D{T1}2 for T < T cr the four coefficients obtained with the best adjusted A-squared values are compared with previous findings. Reduced values for y are confirmed in this work. The results which are well described by the contribution of the DT 5 term to Cp(T) can be connected with the previous Pr-Cu(2) magnetic coupling that is sufficiently enough to cause a modest spin reorientation phase transition at T2 and a critical magnetic behaviour below Tcr .

4 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of magnetic correlations and disorder in a two-dimensional Fermi liquid is considered in connection with the occurrence of the superconducting state, and the electronic mass enhancement has been calculated taking into consideration the magnetic correlation effects and disorder.
Abstract: The influence of magnetic correlations and disorder in a two-dimensional Fermi liquid is considered in connection with the occurrence of the superconducting state. The disorder effect and magnetic correlations work against the superconducting state but at the same time are competitive phenomena. We show that the critical temperature can decrease due to the magnetic correlations and disorder, but the effect of correlations is reduced by the disorder. The electronic mass enhancement has been calculated taking into consideration the magnetic correlation effects and disorder. Its dependence on the concentration impurities, in agreement with the experimental data, shows the importance of the localization effects due to disorder. These results are in agreement with the experimental data obtained for the high critical temperature superconductors.

3 citations

Journal ArticleDOI
TL;DR: In this article, the magnetic and electronic contributions of the Pr ions only to the specific heat C p (T) and entropy S(T) defined by ΔC p and ΔS(T), respectively, are revisited at low temperatures for nonsuperconducting PrBa 2 Cu 3 O 6+x ceramics with x = 1 and 0.95.
Abstract: The magnetic and electronic contributions of the Pr ions only to the specific heat C p (T) and entropy S(T) defined by ΔC p (T) and ΔS(T), respectively, are revisited at low temperatures for nonsuperconducting PrBa 2 Cu 3 O 6+x ceramics with x = 1 and 0.95. Two small anomalies are observed below the well-known anomaly due to the antiferromagnetic (AFM) ordering of the Pr sublattice at the Neel temperature T N = 17.5 and 14 K, respectively. The first one, which occurs near the transition temperature T 2 ~ 10.5 and ~9.5 K, respectively, is due to the effect of the previous spin reorientation phase transition of the Pr moments. Whereas the second one, which appears for both states at the same critical temperature T cr ~ 4-5 K, is caused by the noncollinear magnetic reordering of the Pr subsystem. A phenomenological analysis is used in the fitting procedure below T cr . The values of the associated electronic linear coefficient Δγ are found for both states fairly lower than those deduced from previous measurements on ceramics and single crystals in orthorhombic phase. In addition to the common T 3 contribution to ΔC p (T), which characterizes the Pr AFM ordering, the T 5 contribution associated with the rather significant Pr-Cu(2) magnetic coupling introduces some nonlinear magnetic effects. All results are discussed and compared with earlier reports.

3 citations

Journal ArticleDOI
Fen Liu1, Shixun Cao1, Jincang Zhang1, Lingwei Li1, Changyun Chi1 
TL;DR: In this article, the effects of high valence ions V 4+ and Ni 3+ substitution on superconductivity were studied systematically for the electron-doped superconducting Pr 1.85 Ce 0.15 CuO 4− δ (PCCO) system.
Abstract: Effects of high valence ions V 4+ and Ni 3+ substitution on superconductivity are studied systematically for the electron-doped superconducting Pr 1.85 Ce 0.15 CuO 4− δ (PCCO) system. The results indicate that very small amount of V 4+ substitution ( x ⩽ 0.04) for Cu 2+ site improves the superconductivity, but further substitution ( x ⩾ 0.06) will depress the superconductivity. Contrasting with V 4+ , Ni 3+ substitution shows a strong suppression on superconductivity, even for extremely small amount substitution of 0.01. Both the change of lattice parameters and the similar 3d electron structure of V 4+ ion to the Cu 2+ ion support the improvement of superconductivity while x ⩽ 0.04 in the V-substituted PCCO system. The results of Hall effect indicate that high valence ion substitution for Cu 2+ increase the carrier concentration, which is also one reason for the improvement of superconductivity of V 4+ substitution PCCO.

2 citations