The magnetism of La _1.2 Sr _1.8 Mn ₂ O ₇

Abstract:

The critical behaviour of La_1.2Sr_1.8Mn₂O₇ has been revisited by means of static macroscopic magnetic properties measurements. We present a renewed insight on its equilibrium properties near the critical point ( T _C ∼ 108 K) including the determination of the fundamental characteristics of a magnetic system (anisotropy, critical exponents and crossovers in the vicinity of the Curie temperature). It appears that two-dimensional correlations above T _C do not spread very fast, and that thus the critical fluctuations regime occurs in a moderately narrow temperature range, assessing the three-dimensional nature of the ferromagnetic ordering. The higher temperature contributions to the physical properties, due to stacking defects, are interpreted within the context of the extensive studies carried out on thin films.