Phase stability study of La1.2Ca1.8Mn2O7

We report that the composition of La1.2Ca1.8Mn2O7 does not form as a single phase, and consists of a mixture: of La0.6Ca0.4MnO3 and CaO. The XRD patte rns show the presence of a peak at 2 theta similar to 37 degrees, which is a specific peak to indicate the existence of CaO with space group Fm3m and a unit cell of a = 4.8152(3) Angstrom. After a few days, the intensity of t his peak decreases and CaO transforms to Ca(OH),. The electrical and magnet ic measurements show that the colossal magnetoresistance (CMR) behavior cor responds to that exhibited by La0.6Ca0.4MnO3. (C) 2001 Elsevier Science Ltd . All rights reserved.