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Register a new userMagnetic, electrical and structural properties of the new Re-doped ruthenocuprate Ru1-xRexSr2GdCu2Oy
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Added by
Laura Teresa Corredor Boh\\'orquez
Publication date
2014
fields
Physics
and research's language is
English
Authors
L. T. Corredor
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Despite the discovery of new superconductors classes, high-Tc oxides continue to be a current topic, because of their complex phase diagrams and doping-dependant effects (allowing one to investigate the interaction between orbitals), as well as structural properties such as lattice distortion and charge ordering, among many others. Ruthenocuprates are magnetic superconductors in which the magnetic transition temperature is much higher than the critical superconducting temperature, making them unique compounds. With the aim of investigating the dilution of the magnetic Ru sub-lattice, we proposed the synthesis of the new Ru1-xRexSr2GdCu2Oy ruthenocupratetype family, adapting the known two-step process (double perovskite + CuO)by directly doping the double perovskite, thus obtaining the new perovskite compound Sr2GdRu1-xRexOy, which represents a new synthesis process to the best of our knowledge. Our samples were structurally characterised through X-ray diffraction, and the patterns were analysed via Rietveld refinement. A complete magnetic characterisation as a function of temperature and applied field, as well as transport measurements were carried out. We discuss our results in the light of the two-lattice model for ruthenocuprates, and a relation between RuO2 (magnetic) and CuO2 (superconductor) sublattices can clearly be observed.
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Dependence of superconducting properties of (Ca,RE)(Fe,TM)As2 [(Ca,RE)112, TM: Co, Ni)] on RE elements (RE = La-Gd) was systematically investigated. Improvement of superconducting properties by Co or Ni co-doping was observed for all (Ca,RE)112, which is similar to Co-co-doped (Ca,La)112 or (Ca,Pr)112. Tc of Co-co-doped samples decreased from 38 K for RE = La to 29 K for RE = Gd with decreasing ionic radii of RE3+. However, Co-co-doped (Ca,Eu)112 showed exceptionally low Tc = 21 K probably due to the co-existence of Eu3+ and Eu2+ suggested by longer interlayer distance dFe-Fe of (Ca,Eu)112 than other (Ca,RE)112.
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Study and comparison of over 30 examples of electron doped BaFe2As2 for transition metal (TM) = Co, Ni, Cu, and (Co/Cu mixtures) have lead to an understanding that the suppression of the structural/antiferromagnetic phase transition to low enough temperature in these compounds is a necessary condition for superconductivity, but not a sufficient one. Whereas the structural/antiferromagnetic transitions are suppressed by the number of TM dopant ions (or changes in the c-axis) the superconducting dome exists over a limited range of values of the number of electrons added by doping (or values of the {a/c} ratio). By choosing which combination of dopants are used we can change the relative positions of the upper phase lines and the superconducting dome, even to the extreme limit of suppressing the upper structural and magnetic phase transitions without the stabilization of low temperature superconducting dome.
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