Scanning SQUID Microscopy of Local Superconductivity in Inhomogeneous Combinatorial Ceramics |
| |
| Authors: | Mitra Iranmanesh Dr Manuela Stir Prof Dr John R Kirtley Prof Dr Jürg Hulliger |
| |
| Institution: | 1. Department of Chemistry and Biochemistry, Berne University, Freiestrasse 3, 3012 Bern (Switzerland), Fax: (+41)?31‐631‐42‐72;2. Center for Probing the Nanoscale, Stanford University, Palo Alto, California (USA) |
| |
| Abstract: | Although combinatorial solid‐state chemistry promises to be an efficient way to search for new superconducting compounds, the problem of determining which compositions are strongly diamagnetic in a mixed‐phase sample is challenging. By means of reactions in a system of randomly mixed starting components (Ca, Sr, Ba, La, Y, Pb, Bi, Tl, and Cu oxides), samples were produced that showed an onset of diamagnetic response above 115 K in bulk measurements. Imaging of this diamagnetic response in ceramic samples by scanning SQUID microscopy (SSM) revealed local superconducting areas with sizes down to as small as the spatial resolution of a few micrometers. In addition, locally formed superconducting matter was extracted from mixed‐phase samples by magnetic separation. The analysis of single grains (d<80 μm) by X‐ray diffraction, elemental analysis, and bulk SQUID measurements allowed Tl2Ca3Ba2Cu4O12, TlCaBaSrCu2O7?δ, BaPb0.5Bi0.25Tl0.25O3?δ, TlBa2Ca2Cu3O9, Tl2Ba2CaCu2O8, and YBa2Cu3O7 phases to be identified. SSM, in combination with other diagnostic techniques, is therefore shown to be a useful instrument to analyze inhomogeneous reaction products in the solid‐state chemistry of materials showing magnetic properties. |
| |
| Keywords: | ceramics combinatorial chemistry magnetic properties scanning probe microscopy superconductors |
|
|
