Critical behaviour and magnetocaloric effect of nano crystalline La0.67Ca0.33Mn1−xFexO3 (x = 0.05, 0.2) synthesized by nebulized spray pyrolysis

The structure, critical exponents and magnetocaloric effect (MCE) of Nebulized Spray Pyrolysis (NSP) synthesized nano crystalline La_0.67Ca_0.33Mn_1−xFe_xO₃ (x = 0.05, 0.2) were investigated. The Reitveld refinement of XRD patterns show that the samples adopt an orthorhombic structure with Pnma space group. TEM inspection reveals that the average particle size is about 15 nm and 42 nm for NSP synthesized LCMFe_0.05 and LCMFe_0.2 samples respectively. The temperature and field dependent magnetization studies reveal the superparamagnetic state of La_0.67Ca_0.33Mn_0.95Fe_0.05O₃ and spin-glass-like state of La_0.67Ca_0.33Mn_0.8Fe_0.2O₃. The critical behaviour at the transition region studied using modified Arrott plot provides a second order nature of phase transition for both samples. The magnetocaloric studies show the maximum value of magnetic entropy change (ΔS_max) is in the range 2.3 J kg⁻¹ K⁻¹ at 158 K for LCMFe_0.05 and 0.3 J kg⁻¹ K at 92 K for LCMFe_0.2 respectively at 5 T field. The field dependence of the magnetic entropy changes are also analysed, which show a power law dependence (ΔS_M ∞ Hⁿ, n = 0.72 (2)) at transition temperature, T_C = 162 K for LCMFe_0.05 and n = 1.11(3) at 92 K for LCMFe_0.2.