Effect of potassium doping on the structural, magnetic and magnetocaloric properties of La0.7Sr0.3−xKxMnO3 perovskite manganites

We investigate the effect of potassium doping on the structural, magnetic and magnetocaloric properties of La0.7Sr0.3−xKxMnO3 (x = 0.05, 0.1, 0.15 and 0.2) powder samples. Our polycrystalline compounds were synthesized using the solid-state reaction at high temperature. X-ray diffraction characterizations showed that all our studied samples crystallize in the distorted rhombohedral system with R3¯c space group. With increasing potassium content, the unit cell volume exhibits a broad maximum around x = 0.15. Magnetization measurements versus temperature showed that all our samples exhibit a paramagnetic to ferromagnetic transition with decreasing temperature. The Curie temperature TC is found to decrease from 365 K for x = 0 to 328 K for x = 0.2 as well as the saturated magnetization Msp which shifts from 3.68 μB/Mn for x = 0 to 3.05 μB/Mn for x = 0.2. The critical exponent γ defined as Msp (T) = Msp(0)[1−(T/TC)]γ is found to remain almost constant and equal to 0.33 for all our samples. The maximum of magnetic entropy changes |ΔSmax| of La0.7Sr0.3−xKxMnO3 for x = 0.05 and 0.15 is found to be respectively, 1.37 and 1.2 J kg−1 K−1 under a magnetic field change of 1 T.