Synthesis of High Temperature Superconductive and Colossal Magnetoresistive Surfaces on Insulating Particles
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MAGNETORESISTIVE SURFACES ON INSULATING PARTICLES D. KUMAR, J. FITZ-GERALD AND R. K SINGH Department of Materials Science and Engineering, University of Florida, Gainesville, Florida
32611-6400 ABSTRACT The surfaces of insulating alumina particles have been coated with high temperature superconducting, YBa 2Cu 3O,.x, and colossal magnetoresistive, Pro65 Ba. 05 CqD.3 Mn0%._, films. These
coatings on particulate surfaces have been realized using a new technique which is based on laser assisted generation of homogeneous flux of ablated materials in front of a fluidized bed of host
particles. The coated particulates have been characterized using scanning electron microscopy (SEM), energy dispersive x-ray (EDX) analysis, Auger electron spectroscopy (AES), and
superconducting quantum interference device (SQUID) magnetometer. INTRODUCTION High temperature superconductors (HTSCs) and colossal magnetoresistance (CMR) materials have attracted unprecedented research efforts in the area of electronic materials during the last
decade [1-3].
The structures of both of these materials are pervoskite like [4,5].
The
superconducting properties of HTSCs are associated with Cu-O chains and planes [6] whereas the
magnetoresistive properties of CMR materials are associated with Mn-O planes [7]. Particulate systems coated with HTSC and CMR materials having unique functional properties are well suited
for electrical applications that demand both good magnetic and transport properties [8, 9]. For example, superconducting surfaces on particulate materials can be used inelectromagnetic shielding and particulates coated with colossal magnetoresistive (CMR) material has great potential in ultrahigh-density data storage due to their extremely high sensitivity inmagnetic fields. Particulates coated with these materials can also be excellent soft magnets and yet, because electrons are scattered at the grain boundaries, they would have relatively high electrical resistivity which may result in reduced eddy current losses in electrical applications. In this paper, we report a novel method to synthesize insulating particulates with high temperature superconducting, YBa 2Cu 3O.7 (YBCO), and colossal magnetoresistive, Pr0.65Bao.05C%.3Mn 03.. (PBCMO), surfaces. As indicated by their unit chemical formulae, both of these materials involve multi elements and reproduction of the exact stoichiometry in the coating is very difficult if more commonly used techniques such as sputtering, thermal evaporation or e-beam evaporation are applied [10, 11]. It is in this context that we have used a nanosecond pulsed laser which has emerged as the most successful technique to deal with the problems associated with multi-elemental stoichiometry and homogeneous distribution of the condensate on the substrate materials [12]. The results obtained in the present work have in fact shown that not only the stoichiometry of the elements in coatings are similar to that of target but these coatings also exhibit excellent electrical and magnetic properties.
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