Three-dimensional Ising critical behavior in R0.6Sr0.4MnO3(R=Pr,Nd) manganites

Magnetic as well as calorimetric measurements have been performed on single crystal samples of Pr0.6Sr0.4MnO3 and Nd0.6Sr0.4MnO3 to develop a complete critical behavior study of the paramagnetic to ferromagnetic transition in both manganites. The critical exponents α,β,γ , and δ have been independently obtained. For Pr0.6Sr0.4MnO3, these are α = 0.09, β = 0.312, γ = 1.106, and δ = 4.545, while for Nd0.6Sr0.4MnO3 they are α = 0.11, β = 0.308, γ = 1.172, and δ = 4.75. All these values agree with the three-dimensional (3D)-Ising universality class (α = 0.11, β = 0.3265, γ = 1.237, and δ = 4.79) and are very far away from any other known universality class. This suggests the presence of magnetocrystalline anisotropies in the system that must be taken into account to fully describe the magnetism of these manganites, which deviates from a simple double exchange model