| Sm2-xCexCuO 4-y belongs to a class of materials known as electron-doped superconductors (Ln2- xMxCuO4- y; Ln = Pr, Nd, Sm, Eu; M = Ce, Th) and has a moderately high superconducting critical temperature, Tc, of ∼ 20 K at optimal doping (x = 0.15). The trivalent rare earth site is doped with tetravalent Ce or Th; hence the name "electron-doped". Sm2- xCexCuO4- y also exhibits a unique magnetic structure at low temperatures (T < 6 K) due to the antiferro-magnetic ordering of the Sm3+ ions. In this study, thin films of the electron-doped superconductor Sm 2-xCexCuO 4-y (SCCO) have been grown by pulsed laser deposition (PLD) for a cerium concentration range of x = 0.13 to x = 0.19. The films have been characterized through x-ray diffraction, electrical transport, and thermal transport measurements. A temperature versus cerium content (T-x) phase diagram has been constructed from the electrical transport measurements and yields a superconducting region similar to that of two of the other electron-doped superconductors Nd2-xCe xCuO4-y and Pr 2-xCexCuO 4-y. Thermopower measurements were also performed on the samples and show a dramatic change from the under-doped region (x < 0.15) to the overdoped region (x > 0.15). Additionally, the standard Fisher-Fisher-Huse (FFH) vortex glass scaling model has been applied to the magnetoresistance data, as well as a modified scaling model (RRA), and the analysis yields values of the vortex glass melting temperature, T g, and critical exponent, nu(z-1). A magnetic field versus temperature (H-T) phase diagram has been constructed for the films with cerium content x ≥ 0.14, displaying the vortex glass melting lines. Magnetoresistance data taken as a function of angle, theta, is also discussed in the context of the vortex glass scaling model. |
