Chemical and Magnetic Study of Layered Strontium Lanthanum Manganate Structures

Abstract

Previously published work describes the magnetic properties of the calcium manganate (IV) phases having tetragonal structures consisting of perovskite layers separated along the 001 direction by non-magnetic layers. Anomalous magnetic behavior exhibited by these was attributed to a persistence of short-range, two-dimensional order above the Néel temperature. In the present study, phases having similar structures were prepared having the general composition SrO[(Sr1−xLaxMnx3+ Mn1−x4+)O3]y, where y = 1, 2, 3 corresponding to single, double, or triple perovskite layers. Magnetization measurements over the range 1.4°–300°K showed that ferromagnetism expected of the Mn3+-O-Mn4+ interaction was achieved. At low temperatures, remanent moments as high as 3.2 μB/MN ion were observed. With increasing temperatures, these decreased in an anomalous manner. At intermediate temperatures there was a sharp decrease-like that expected at a Curie temperature. However, at its termination a significant moment remained. This behavior is thought to be related to the two-dimensional nature of these layered structures and may depend upon a long spin-correlation length which is expected of such structures.