We report on the reproducible growth of stoichiometric thin films of ferromagnetic intermetallic compound NiMnSb by pulsed laser deposition (PLD) on various substrates. The films are grown at moderate temperature (around 200 degree(s)C) using polycrystalline targets. Two different substrates were employed - single crystalline silicon and InAs polycrystalline - to investigate the influence of the thin layer/substrate lattice mismatch on the quality of the grown film. XRD and EDX analyses indicate that the layers are of high crystalline quality and their stoichiometry is very close to that of the corresponding targets, respectively. SEM images show that there are droplets on the surface of the films and their composition is similar to that of the targets. Magnetic measurements performed at both room temperature and 5K find that the investigated samples have small Hc values.
H. Ding, M. Norman, John Giapintzakis, Juan Campuzano, H. Claus, H. Wuehl, M. Randeria, A. Bellman, T. Yokoya, Takashi Takahashi, Takashi Mochiku, Kazuo Kadowaki, Don Ginsberg
Using high resolution angle-resolved photoemission spectroscopy (ARPES), we measure the superconducting gap and its momentum dependence in the high temperature superconductors Bi2Sr2CaCu2O8 (Bi2212) and YBa2Cu3O6.95 (Y123). It is found that umklapp bands due to the incommensurate superlattice in Bi2212 may obscure the intrinsic momentum dependence of the gap. By taking these into consideration, we find a d- wave-like gap function in Bi2212. We also report an unambiguous observation of the superconducting gap in Y123.
Evidence of micron-sized structural inhomogeneities in several high transition temperature (Tc) superconductors is presented. By illuminating samples with high energy, highly collimated x rays produced on a synchrotron wiggler, small changes in the lattice were detected over a spatial scale as small as 10 micrometer. In the YBa2Cu3O7-(delta ) crystals, these changes are interpreted as evidence of variations in the oxygen content and in the Nd2-xCexCuO4-y crystal, as a variation in the cerium content. Each type of inhomogeneity can affect the superconducting properties.
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