Reentrant spin glass behavior in CE-type AFM Pr0.5Ca0.5MnO3 manganite

The magnetic and transport properties of Pr0.5Ca0.5MnO3 with a CE-type antiferromagnetic structure were systematically investigated. A distinctive sequence of multiple magnetic transitions is found: paramagnetic (PM)-ferromagnetic (FM)-antiferromagnetic (AFM)-spin glass (SG) transitions. The results show that the low-temperature SG state is different from a conventional SG but has a reentrant character. The reentrant SG behavior accompanied with colossal magnetoresistance might be due to the competing interaction between FM and the CE-type AFM matrix. Also, this phase may be related to the disorder due to the variance of tolerance factor I and characteristic parameter sigma(2) (reflecting A-site cation size variance). Meanwhile, this kind of reentrant SG state exists in most manganites and it shows a complex magnetic ground state. The present experimental data establishes that Pr0.5Ca0.5MnO3 compound shows the coexistence of FM clusters and SG clusters in the background of an AFM matrix. Here, all the rich variety of phases can be explained by the bandgap modified locally by strain within each grain. At the same time, the present results indicate also that Pr0.5Ca0.5MnO3 has a ground state, which shows the presence of some FM clusters in the background of the remaining region in a spin frozen state. The RSG phenomena should be a universal characteristic of manganites with CE-type AFM structure and it is very sensitive to the subtle disorder. (c) 2005 Elsevier B.V. All rights reserved.