Defect induces effect on LaCoO3: From diamagnetism to ferrimagnetism due to vacancy in the bulk lattice

LaCoO3 suffers spin crossover as a function of temperature, changing from low-spin state to intermediate-state and, at high temperatures, it also changes to a high-spin state. Nano-confinement of this material induces a long-range magnetic ordering, with a critical temperature close to 83 K; and to deepening this debate whether it is a consequence of nanotopology or defects on the surface, we have prepared the compositions of the series La1−x□xCo1−x3+Cox4+O3 (x=0.00, 0.04, 0.08 and 0.12). We experimentally found an axial compression of the CoO6 octahedra, verified by the new elasticity parameter σ; and, based on the Jahn-Teller theorem, we proposed a spin state and a mean-field model, that successfully fitted the experimental magnetic susceptibility. As an output, we found that the Co(III) sub-lattice has an antiparallel intra-lattice alignment; while the Co(IV) sub-lattice has a parallel intra-lattice alignment. As a part of the ferrimagnetic model considered, the net magnetization of both sub-lattices (Co(III) and Co(IV)), are aligned in opposition. The magnetic behavior of these vacant bulk samples is similar to those nanostructured ones, with the same critical temperature, and therefore we claim that the long-range magnetic ordering found for those nanomaterials has its origin on the Jahn-Teller effect on the surface of the sample.