Structural, magnetic, magnetocaloric, investigations on La0.8−xKxSr0.2Mn0.95Ni0.05O3 (x = 0.05, 0.10 and 0.15) at room temperature.

• As the K concentration increases from 0.05 to 0.15, the Tc of the sample gradually increases. In A site doping, the Curie temperature (Tc) of La 0.75 K 0.05 Sr 0.2 Mn 0.95 Ni 0.05 O 3 is nearer to room temperature. The Tc of La 0.75 K 0.05 Sr 0.2 Mn 0.95 Ni 0.05 O 3 sample is 305 K. • We use Banerjee's criterion and phenomenological universal curves to prove that the paramagnetic-ferromagnetic (PM-FM) transformation of the samples is a second order magnetic phase transition. • The K+ doped La 0.7 K 0.1 Sr 0.2 Mn 0.95 Ni 0.05 O 3 sample has a maximum magnetic entropy change of 4.11 J/kg K at a temperature of 315 K, and its RCP is 288.15 J/kg under external magnetic field variation. This material can potentially be one of the candidates that can be used to develop the magnetic refrigeration technology. • By comparing with other magnetic materials, we know that La 0.8-x K x Sr 0.2 Mn 0.95 Ni 0.05 O 3 (x = 0.05, 0.10, 0.15) samples have large magnetic entropy change and RCP compared to other magnetic materials. Indicating that the samples have good potential for magnetic refrigeration applications. This paper investigated the effect of A-site doping K+ on the structural, morphological, and magnetic properties of La 0.8 Sr 0.2 Mn 0.95 Ni 0.05 O 3. La 0.8-x K x Sr 0.2 Mn 0.95 Ni 0.05 O 3 (LKSMNO) were synthesized by the sol–gel (S–G) method. The XRD analysis and refinement have revealed that LKSMNO were the rhombohedral structure of the R-3c space group (No. 167) and the cell volume increased with increasing K+ doping. The ratio of Mn4+/Mn3+ becomes larger with the increase of K+ content. The magnetic studies indicate that the Curie temperature (TC) of LKSMNO increases from 305 K to 320 K with the increase of K+, and the second order magnetic phase transition occurs around the TC. When the external magnetic field (H) is 5 T, the maximum magnetic entropy changes (- Δ S M m a x ) were 4.00 J/(kg K), 4.11 J/(kg K), and 3.39 J/(kg K), respectively, near TC. The relative cooling power (RCP) of LKSMNO were 272.28 J/kg, 288.15 J/kg, and 304.90 J/kg. [ABSTRACT FROM AUTHOR]