• Comment on magnetism and superconductivity in rutheno cuprates: RuSr2GdCu2O8 and RuSr2Gd1.5Ce0.5Cu2O10

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      https://www.ias.ac.in/article/fulltext/pram/058/05-06/0809-0815

    • Keywords

       

      Magnetic superconductor; rutheno cuprates; structural analysis; microstructure

    • Abstract

       

      Both RuSr2GdCu2O8-δ (Ru-1212) and RuSr2Gd1.5Ce0.5Cu2O10-δ (Ru-1222) exhibits magnetism and superconductivity, as seen by magnetization vs. temperature behavior measured in 5 Oe field. Zero-field-cooled (ZFC) and field-cooled (FC) magnetization data show branching at around 140 K and 100 K with a cusp at 135 K and 80 K and a diamagnetic transition around 20 K and 30 K in the ZFC part, for Ru-1212 and Ru-1222, respectively. The isothermal magnetization possesses a non-linear contribution due to a ferromagnetic component at low temperatures below 50 K for both samples. The resistance vs. temperature behavior of the samples in applied fields of 0, 3 and 7 T confirmed superconductivity, with a different type of broadening of the superconductivity transition under magnetic fields for Ru-1212 from that known for conventional high-Tc superconductors. The magnetoresistance (MR) is negative above the Ru magnetic ordering temperature at 135 K. Below the Ru magnetic ordering temperature, MR displays a positive peak at low fields and becomes negative at higher fields for Ru-1212. For Ru-1222, MR remains negative both above and below the ordering temperature. A maximum of 2% is observed for the negative MR value at the Ru magnetic ordering temperature. An electron diffraction pattern obtained for the Ru-1212 sample shows two types of superstructure: one has a weak spot at the centre of the a–b rectangle, and the other only along the b direction. Interestingly, Ru-1222 shows only clean a–b and a–c planes, without any superstructures.

    • Author Affiliations

       

      VPS Awana1 M Karppinen1 H Yamauchi1

      1. Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama - 226-8503, Japan
    • Dates

       
  • Pramana – Journal of Physics | News

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