Tricritical behavior and Griffith phase in La_1-xCa_xMnO₃ under high applied fields

Studying the magnetic property of La_0.7Ca_0.3MnO₃ (LCMO) bulks, it has been found that they exhibit a first-order phase transition (FOPT) around the ferromagnetic-paramagnetic (FM-PM) transition. However, most previous studies just concerned on their magnetic property for applied fields below 60 kOe. To learn more about this material system, we have considered the influence of high applied fields up to 140 kOe on the magnetic property of a polycrystalline LCMO bulk sample. The detailed analyses based on the Banerjee criterion, Arrott and Kouvel-Fisher methods, and scaling hypothesis prove LCMO exhibiting the first-order phase transition at low applied fields (H) and the tricritical behavior at high applied fields H > 65 kOe with critical exponents β ≈ 0.25 and γ ≈ 1 close to those expected for the tricritical mean-field theory. We have also found a strong dependence of the FM-PM transition temperature (T_C) on H varying as a power function T_C(H) ∝ Hⁿ (with n = 0.64 and H > 3.5 kOe), and an existence of the Griffiths phase that is completely suppressed as H ≥ 35 kOe.