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The effects of K+ doping on structure, magnetic characteristics, magnetocaloric properties, and critical behavior of La 0.7-x Nd 0.1 Sr 0.2 K x Mn 0.95 Ni 0.05 O 3 (LNSKMNO) ceramics (x = 0.00, 0.05, and 0.10) were investigated. The X-ray diffraction and refinement findings revealed that LNSKMNO exhibited a distinctive rhombohedral structure of the R-3c space group (No. 167). To validate the chemical composition of LNSKMNO ceramics, EDS spectroscopy and X-ray photoelectron spectroscopy (XPS) were utilized. The magnetization of LNSKMNO exhibited a temperature-dependent behavior, revealing a phase transition from the ferromagnetic (FM) phase to the paramagnetic (PM) phase at approximately the Curie temperature (Tc). By utilizing normalization and Banerjee's criterion, the magnetic phase transition of LNSKMNO was determined to be a second order magnetic phase transition. The maximal magnetic entropy (− Δ S M max) of LNSKMNO around Tc was 4.24, 4.53, and 4.07 J/(kg K) at the 5 T external magnetic field (H). The Kouvel-Fisher approach and modified Arrott plot were used for determining the values of the critical exponents of β , γ , and δ. The critical exponents for LNSKMNO ceramics generally conformed to those obtained based on the Mean-field model. [ABSTRACT FROM AUTHOR]