Use of AC susceptometry to study magnetoresistive properties of ceramic samples

Summary form only given. Studies to establish the relationship between electronic transport properties and the magnetic response in colossal magnetoresistive (CMR) polycrystalline manganites, have been a permanent concern in the specific literature. It is well-known that, in the magnetoresistive phenomenon, conformance and particle size act as crucial parameters, providing a link between transport and magnetic properties. It is well understood that magnetoresistance effects in ceramic materials have two contributions. One, the so-called intragranular component, whose origin seems to be related to spin fluctuations, occurs just below the critical transition temperature T/sub C/, being related to the intrinsic properties of the material. The other, usually referred to as the intergranular part, might be related to spin-polarized tunneling between grains and is highly dependent on the interfaces between neighbors, being thus an extrinsic, processing-dependent characteristic. In this contribution we present results obtained from AC susceptibility and transport measurements, in a series of samples specially prepared and treated for this purpose. Samples of the optimized CMR manganite (LCMO) have been produced using the Modified Polymeric Precursors Method. The studied specimens have been prepared using different procedures, in order to evidence inter and intragranular characteristics.