Spin polarized tunneling spectroscopy of intercalated Bi2Sr2CaCu2O8+

Abstract

There has been continuing interest in decades in heterostructure tunnel junctions that combine ferromagnetic material (F), insulator (I) and superconductor (S). This junction has been known to a good probe to analyze the physical properties of ferromagnetic and superconducting materials. In order to understand the influence of the spin injection on the c-axis tunneling characteristics of a Bi-2212 single crystal as a function of temperature and magnetic field, two sets of samples have been prepared; in one set, the surface of HgBr2 intercalated Bi-2212 crystals have been deposited with merely Au while the other set has ferromagnetic multilayer (Au/Co/Au) on top of the crystal. The micron sized mesa arrays have been patterned using photolithography and ion beam etching techniques. The surface topography and height of the mesa were investigated using atomic force microscopy. Tunneling characteristics were examined by means of the novel technique, point contact tunneling (PCT), and experiment were performed wide range of temperatures from 4.2 K to 300 K and that of magnetic field from 0 G to 2600 G. The results of spin polarized tunneling measurements compared with spin degenerate tunneling. Magnetic field dependence hysteretic I-V curves with multiple branches were examined to show the suppression of the superconductivity with spin polarized current. The distinct temperature dependence of depression in tunneling conductance near Fermi level was discussed for spin degenerate and polarized currents above Tc. The zero bias conductance and resistivity versus temperature plots were investigated to show the existence of the pseudogap in tunneling spectroscopy of investigated samples.