Effects of Cr3+ incorporation on structure, surface morphology, and the magnetocaloric effect in La0.8Sr0.2Mn1-xCrxO3 ceramics by means of first-principles calculations and wet chemical method

The investigation focused on the impact of Cr 3+ incorporation on structural features, surface morphology, and the magnetocaloric effect in La 0.8 Sr 0.2 Mn 1- x Cr x O 3 ceramics, with x values of 0.05, 0.10, and 0.15, employing both experimental methods and theoretical simulations. Synthesis of La 0.8 Sr 0.2 Mn 1- x Cr x O 3 ceramics was achieved using the sol-gel method. Analyses via transmission electron microscopy and X-ray diffraction confirmed that La 0.8 Sr 0.2 Mn 1- x Cr x O 3 ceramics possess a rhombohedral crystal structure, corresponding to space group No.167 (R-3c). Scanning electron microscopy revealed that La 0.8 Sr 0.2 Mn 1- x Cr x O 3 ceramics comprise irregular ellipsoidal particles. The average particle size ranged from 173 nm to 226 nm. XPS confirmed the presence of all elements in La 0.8 Sr 0.2 Mn 1- x Cr x O 3 ceramics. Mixed valence states of Mn (Mn 3+ /Mn 4+ ) and Cr (Cr 3+ /Cr 4+ ) were identified, with Sr at +2 and La at +3. The Tc of La 0.8 Sr 0.2 Mn 1- x Cr x O 3 ceramics ( x  = 0.05, 0.10, 0.15) were determined using a Magnetic Property Measurement System to be 301 K, 278 K, and 253 K, respectively. A decrease in Tc with increasing Cr 3+ doping was observed. Analysis of isothermal magnetization and Arrott plots reveals that La 0.8 Sr 0.2 Mn 1- x Cr x O 3 ceramics undergoes a second-order transition from paramagnetism to ferromagnetism. It was found that the net magnetic moment (The vector sum of all magnetic moments) and magnetic entropy change of La 0.8 Sr 0.2 Mn 1- x Cr x O 3 ceramics decreased with increasing of Cr 3+ doping. For samples with a chromium doping level of x  = 0.05, the Tc is recorded at 301 K. At this doping concentration, the peak magnetic entropy change is observed to be 3.50 J/(kg K) (H = 5 T).