MagnetIc Properties of LaO.85CaO.15Mn1-yFey03 (O<y<O.08) CMR Compounds

Abstract

This work reports the development of magnetic phases in a colossal magnetoresistance (CMR) compound Lao.8sCao I5Mnl _yFey0 3 upon doping with Fe ions. Lying near the antiferromagnetic-ferromagnetic phase boundary, the initially ferromagnetic system is observed to undergo two successive transitions on the addition of Fe ions viz a ferromagnetic one at higher temperatures followed by a reentrant spin glass transition at lower temperatures. The study has been performed by using the technique of linear and non-linear AC response both in zero and applied DC fi elds. For the purpose of the study an AC susceptometer has been designed and constructed that enables sensitive measurements down to 10K. The measurement of both the second (even) and third (odd) harmonics have been carried out and their field dependence has been analyzed to show how the application of the DC field stabilizes the ferromagnetic moment in the low temperature spin glass state. We suggest that the system undergoes a phase separation into ferromagneti c and antiferromagnetic regions that at lower temperatures appears as a spin glass type state