Phase Diagram and Weak-link Behavior in Nd-doped CaFe_2As_2

Abstract

The transport properties, phase diagram, and dopant distribution are investigated in systematically Nd doped CaFe_2As_2 single crystals. Coexistence of two superconducting (SC) phases with different critical transition temperature (T_c) is observed. The low-T_c phase emerges as x >= 0.031, and the T_c value increases to its maximum value of about 20 K at x = 0.083, the maximum doping level in our study. As x >= 0.060, the high-T_c phase with a T_c value of about 40 K is observed. The structure transition (STr) from tetragonal to orthorhombic phase vanishes suddenly around x = 0.060, where a new STr from tetragonal to collapsed tetragonal phase begins to turn up. Compared to the low-T_c phase, the end point of SC transition of the high-T_c phase is more sensitive to the magnetic field, showing a characteristic of Josephson weak-link behavior. Possible scenarios about this system are discussed based on our observations. We also find that the non-uniform SC properties cannot be attributed to the heterogeneous Nd distribution on the micro scale, as revealed by the detailed energy dispersive X-ray spectroscopy (EDS) measurements.

12 pages, 5 figures

References in corpus (12)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Superconductivity at 22 K in Co-doped BaFe2As2 Crystals
• Spin density wave anomaly at 140 K in the ternary iron arsenide BaFe2As2
• Determination of the phase diagram of the electron doped superconductor Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Pressure-induced volume-collapsed tetragonal phase of CaFe2As2 as seen via neutron scattering
• Superconductivity induced by Ni doping in BaFe${}_2$As${}_2$
• Iron based high transition temperature superconductors
• Phase Diagram of Ba1-xKxFe2As2
• Lattice collapse and quenching of magnetism in CaFe2As2 under pressure: A single crystal neutron and x-ray diffraction investigation
• Growth and characterization of A_{1-x}K_xFe_2As_2 (A = Ba, Sr) single crystals with x=0 - 0.4
• The B -> D* l nu form factor at zero recoil from three-flavor lattice QCD: A model independent determination of |V_cb|
• Transport and magnetic properties of La-doped CaFe${}_2$As${}_2$