K dopant effect on ${\hbox {La}}_{0.7}{\hbox {K}}_{x} {\hbox {Ca}}_{0.3-x}{\hbox {MnO}}_{3}$ ($x=0,$ 0.05, 0.1) perovskite compounds: the structural, magnetic and magnetocaloric properties

Abstract

${\hbox {La}}_{0.7}{\hbox {K}}_{x}{\hbox {Ca}}_{0.3-x}{\hbox {MnO}}_{3}$ ($x=0,$ 0.05, 0.1) perovskites were prepared by sol–gel method. The K-doped effect was determined by the structural, magnetic, and magnetocaloric properties of the compounds. In the crystal structure of K-doped ${\hbox {La}}_{0.7}{\hbox {Ca}}_{0.3}{\hbox {MnO}}_{3},$ Mn–O–Mn bond angle slightly increases with K addition. The transition shifts the range of 270–320 K when the K is added in ${\hbox {La}}_{0.7}{\hbox {Ca}}_{0.3}{\hbox {MnO}}_{3}.$ The Curie temperature increases from 251 to 288 K with increasing K amount. The maximum magnetic entropy change was found to be 2.7 J kg$^{-1}\,{\hbox {K}}^{-1}$ at 283 K under a magnetic field change of 2 T for the ${\hbox {La}}_{0.7}{\hbox {K}}_{0.05}{\hbox {Ca}}_{0.25}{\hbox {MnO}}_{3}.$ The relative cooling powers (RCPs) in the ${\hbox {La}}_{0.7}{\hbox {K}}_{x}{\hbox {Ca}}_{0.3-x}{\hbox {MnO}}_{3}$ ($x=0,$ 0.05, 0.1) samples were calculated to be 103, 133 and 88 J kg$^{-1},$ respectively.