A large magnetocaloric effect of La0.8Na0.2Mn0.97Bi0.03O3 manganite synthesized by pechini Sol-Gel method and compared to the sample synthesized by solid-state route.

Highlights • We showed the crystallization of the compounds in the rhombohedra structure with R-3c space group. • The Curie temperature decreases with the reduction of the crystallite size. The obtained values are 320 K and 257 K for S1 and S2, respectively. • We proved that the values of – ΔSmax at a 5 Tesla applied magnetic field are 5.88 J/Kg·K and 4.73 J/Kg·K for S2 and S1, respectively. • The study of the critical phenomena showed that the Tricritical mean field model describes S2 and S1 is interpolated between the Tricritical mean field model and 3D- Heisenberg model. Abstract In this work, the physical properties of the compounds La 0.8 Na 0.2 Mn 0.97 Bi 0.03 O 3 prepared by solid-state (S1) and Sol-Gel (S2) methods are compared. Both compounds were found to crystallize in the rhombohedra structure with R-3c space group. They also exhibited a Ferromagnetic (FM)-Paramagnetic (PM) phase transition around the Curie temperature (T C). Curie temperature T C and magnetization decreased with the decrease of the crystallite size. The maximum of the magnetic entropy change ΔS M at 5 T, were about 4.73 J·K−1·kg−1 and 5.88 J·K−1·kg−1 for S1 and S2, respectively. We proved the second order character via the normalization curves and through the Banerjee criteria. Moreover, we determined the critical exponents values of β, γ and δ with the extrapolation of Arrott plots, the Kouvel fisher technique and the critical isotherm, respectively. The validity of the exponents values was confirmed with the scaling hypothesis; the M (T, ε) curves collapsed onto two independent universal branches below and above Tc. [ABSTRACT FROM AUTHOR]