Spin-Polarized Tunneling Study of Spin Effects in the Superconducting State

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9424467 Tedrow The discovery of spin-polarized electron tunneling has made possible detailed probing of the superconducting state in the presence of applied magnetic fields to an extent not previously possible. In particular, the development of tunnel barriers that act as spin filters has greatly increased the versatility of this technique. In this work, the spin-polarized tunneling technique will be applied to the investigation of the density of states of thin-film superconductors in three regimes of external influence. In the first regime, the superconductor will be subjected to injection of quasiparticles through a spin-filter tunnel barrier to allow observatio of possible spin-dependent nonequilibrium effects. In the second, spin state mixing caused by spin-orbit scattering and magnetic exchange interactions arising in rare-earth impurities will be studied. Finally, the exchange proximity effect will be used along with the tunneling spectroscopy to attempt to verify the existence of the Fulde-Ferrell-Larkin-Ovchinnikov state. %%% Experiments are proposed to study the distribution of conduction electron energies (the so-called "density of states") in thin-film superconducting materials by means of the experimental technique of spin-polarized electron tunneling. In this technique, electrons of one spin (magnetic moment) orientation "tunnel" preferentially through an insulating magnetic barrier into the superconductor; the resulting current provides a map of the electron energies in the superconductor. Further information will be gained by studying these effects under the influence of external magnetic fields and in the presence of magnetic impurity atoms doped into the superconducting films. ***