ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
A series of polycrystalline La0.7−xYxCa0.3MnO3 samples were studied, where x=0, 0.07, 0.1, 0.15, and 0.2. Measurement of the dc resistivity, microwave surface resistance, ac susceptibility, and dc magnetization were made. As expected, the magnetic state becomes more frustrated as Y is added. It is found that the dc resistivity is approximately two orders of magnitude larger than the 9 GHz resistivity for all samples, however, both increase with Y doping by the same multiplicative factor. From circumstantial evidence and estimation of the grain boundary response time, it is found that the microwave measurement short circuits the grain boundaries. We assume that the dc resistivity is dominated by grain boundary properties and the microwave resistivity reflects intragranular behavior. Analysis of the electrical transport at dc and microwave frequencies is carried out and a phenomenological model proposed which agrees well with observation. The model implies that the influence of Y is modified by the underlying static disorder in which it is placed. © 2000 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1289522
