Magnetism and critical behavior of double perovskite RE2CoMnO6 (RE = La and Eu) compounds

•The magnetic properties in RE2CoMnO6 (RE = La and Eu) were investigated.•The critical parameters for RE2CoMnO6 (RE = La and Eu) were determined.•Both compounds are close to the long-range mean-field theoretical model. The magnetic properties and critical behavior near the Curie temperature TC in the double perovskite RE2CoMnO6 (RE = La and Eu) were systematically investigated via the modified Arrott plots (MAP), the Kouvel-Fisher plot (K-F), and the critical isotherm analysis (CI). The reliable value of critical parameters (β, δ, and γ) obtained from K-F plot are to be 0.4704, 0.9978, and 3.12 with TC of 210.8 K for La2CoMnO6, and to be 0.6065, 0.9237, and 2.52 with TC of 130.3 K for Eu2CoMnO6, respectively. Moreover, the reliability of critical parameters of two samples was further verified by different methods including the Widom scaling relation and the magnetic equation. The obtained values of critical parameters are all close to the value of the mean-field theoretical model which manifested the presence of the long-range FM order for RE2CoMnO6 (RE = La and Eu) compounds.