Potential giant magnetoresistance perovskites: The manganites La1−xAx+MnO3 (A+=K+, Na+, Rb+, Ag+, Tl+, Cu+, and Li+) (abstract)

Rare-earth alkaline earth substitute manganites perovskites, Ln1−xAx2+MnO3 (A=Ca, Sr, Ba, Pb), have retained considerable attention in regard to their colossal magnetoresistance coefficient for compositions in the range 0.1⩽x⩽0.4. Compounds where A2+ cations replaced monovalent A+ cations such as K+ Ag+, etc., have been known for a long time1 and have even been tested as oxidation catalysts for exhaust gazes of internal combustion engines. Surprisingly enough, however, they have given rise to very little investigation as potential giant MR candidates. Preliminary structural features (cell distortions), magnetic and electric properties versus temperature are presented for the series of compounds of general composition La1−xAx+Mn1−2x3+Mn2x4+O3, where A+=Rb, K, Na, Ag, Tl, Cu, and Li. Lanthanum can be partly or totally replaced by Pr, Nd or other rare-earth cations or yttrium. Most of the phases of the lanthanum subseries are rhombohedral (R-3c) and ferromagnetic. Curie temperatures are strongly dependent on...