Two-dimensional magnetic interplay in the tensile-strained LaCoO3 thin films

Abstract

High-quality epitaxial LaCoO₃ (LCO) thin films have been deposited on SrTiO₃ (STO) substrates with pulsed laser deposition (PLD). We find that the LCO films undergo a typical ferromagnetic–paramagnetic (FM–PM) phase transition at ∼80 K. To understand the nature of magnetic phase transition, various methods, including the modified Arrott plot and critical isotherm analysis, were used to determine the critical exponents, which are β = 0.754(1) with a Curie temperature T_C = 79.8(8) K and γ = 1.52(2) with T_C = 79.9(2) K. The reliability of these critical exponents was confirmed using the Widom scaling relation and the scaling hypothesis. Further analysis revealed that the spin coupling within the LCO films exhibits two-dimensional (2D) long-range magnetic interaction and the magnetic exchange distance decays as J(r) ∼ r^−(3.46). Our critical behavior analysis may shed new light on the further understanding of the origin of FM and the relatively fixed T_C in LCO thin films.