Superconductivity and Stoichiometry in the BSCCO-family Materials

We report on magnetization, c-axis and ab-plane resistivity, critical current, electronic band structure and superconducting gap properties. Bulk measurements and photoemission data were taken on similar samples.Comment: 4 pages, latex, to be published in Journal of Superconductivity. two figures available from Jian Ma at [email protected]

Laser CVD and Plasma CVD of CRO\u3csub\u3e2\u3c/sub\u3e Films and Cobalt Doped CRO\u3csub\u3e2\u3c/sub\u3e Films Using Organometallic Precursors

Chromium dioxide is deposited as a ferromagnetic layer onto selected portions of a substrate or over the entire substrate. Chromium hexacarbonyl vapor is introduced into a vacuum deposition chamber at e.g. 10 milliTorr and oxygen is introduced at e.g. 15 to 100 milliTorr. A UV laser beam is focused onto the substrate to form the CrO2 layer photolytically. The CrO2 layer can also be deposited by RF plasma deposition. This technique can also be employed for depositing MoC2, WC2, Mo2φ3, MoO2 or WO2. Magnetic recording or memory devices are produced without the high failure rate typical of the prior art sputtering technique

A spin-polarized He (2³S₁) metastable atom source for surface research

Text includes handwritten formulasSurface science has a paucity of probes, particularly for spin-dependent studies. This thesis describes a 2 3S1 He probe, recently developed in this laboratory, that can be used for such investigations. There are three interaction mechanisms such a probe can undergo: resonance ionization/ Auger neutralization, Auger deexcitation, or surface Penning ionization. All are discussed and compared. The important concepts introduced include electronic transitions, factors affecting the interactions, variation of atomic energy levels, and the convolution problem. After introducing these concepts, and describing the resulting physical phenomena, the experimental apparatus is examined. The thesis delineates the rationale for a multi-chamber design and the problems encountered. One diagnostic, a Stern-Gerlach magnet used as a polarization analyzer, is particularly useful and is described in detail. By using the analyzer, we found the beam is approximately 5 percent polarized. Finally, several problems related to the first experiments are discussed

METASTABLE DEEXCITATION SPECTROSCOPY: A NEW PROBE OF SURFACE MAGNETISM

A new method, described herein, has been developed for probing magnetic and other spin-dependent surface properties. The technique utilizes a He 2 ('3)S(,1) beam in which a plurality of atoms is in one m(,J) level. This electron spin polarized beam has been used to probe the surface magnetic properties of a clean and adsorbate-covered Ni (110) crystal. The electrons ejected from the sample when the metastables deexcite depend upon metastable polarization and sample magnetization. By examining the ejected electrons, the sample magnetization has been measured as a function of electron energy, crystal temperature, and adsorbate (CO) coverage. The results demonstrate that He 2 ('3)S(,1) metastables constitute a method for probing surface magnetism with unparalleled surface specificity. In addition to discussing the physics of the metastable/surface interaction and the results obtained, the theoretical background and a perspective of surface spectroscopies are provided in sections on magnetism and other surface spectroscopies