Finite size effects and the effect of disorder on electronic phase separation in Pr_(0.5)Ca_(0.5)Mn_(1-x)Al_(x)O_(3)

摘要

We report a bulk magnetisation study of the low temperature magnetic phasesin the Mn site substituted half doped manganite seriesPr_(0.5)Ca_(0.5)Mn_(1-x)Al_(x)O_(3). Our results indicate the formation of selforganised structures in this series of compounds which is driven by electronicphase separation and stabilised by the presence of finite quenched disorder,thus providing a basis for understanding the anomalously large supression ofthe CE phase in the presence of disorder. Striking magnetic memory effectssimilar to that seen in spin glasses and interacting superparamagnets are alsoobserved. Increasing disorder is seen to make electronic phase separationweaker owing to the destabilisation of the CE state which results in anenhanced mobility of the charge carriers.