Analysis of the magnetization and the inverse susceptibility near the Curie temperature in double perovskite

The temperature dependences of the magnetization M and the inverse susceptibility χ–1 are analyzed by the power-law formulae with the critical exponent's order parameter β and susceptibility γ, respectively, for the double perovskites R2NiMnO6 (R = Dy, Ho, and Er) close to the ferromagnetic–paramagnetic (FM–PM) transition using the literature data. Values of the critical exponents β and γ are also determined by the Kouvel–Fisher method near the Curie temperature TC for the FM–PM transition in those double perovskites. Additionally, the magnetic field H dependence of the magnetization M is analyzed (at T = TC) by the power-law formula with the critical isotherm exponent δ for the studied perovskites. The Widom scaling relation among the critical exponents β, γ, and δ is examined for these structures. The obtained values of the critical exponents β, γ, and δ are in good agreement to some extent, depending on the temperature and field intervals in the analysis, with the predicted values of the mean field, tricritical mean field, and 3D Ising and 3D Heisenberg models.