Critical Behavior of the (111)-Oriented LaCoO3/SrTiO3 Thin Film

Apart from the impact of different substrates on epitaxial thin films due to lattice constant mismatches, the properties of epitaxial thin films are also influenced by the same substrates with different crystal orientations. Herein, the (111)-oriented SrTiO3 (STO) substrates are used to fabricate the LaCoO3 (LCO) epitaxial thin films rather than the more common (001)-oriented STO substrates. It undergoes one paramagnetic-ferromagnetic phase transition around 50 K. This phase transition is similar to the previously observed for (001)-LCO/STO, but the Curie temperature (T (c)) is significantly lower than the previously reported 80 K. To investigate the decrease of T (c) and gain further insight into the phase transition, the critical behavior analysis of thin film is performed. The critical exponents are determined to be beta = 1.591(3) and gamma = 0.937(1) by reconstructing a modified Arrott plot, and the reliability of these exponents is confirmed by the Widom scaling relation. Using the renormalization group theory approach, it is discovered that the film has a long-range magnetic interaction with space dimensionality d = 2 and spin dimensionality n = 1, and the magnetic exchange interaction decays J ( r ) approximate to r - 2.4473 .