The investigation of the effect of K doping on the structural, magnetic, and magnetocaloric properties of La1.4-xKxCa1.6Mn2O7 (0.0 <= x <= 0.4) double perovskite manganite

Abstract

In this study, the effect of potassium doping on the morphological, crystallographic, magnetic and magnetocaloric properties of La1.4Ca1.6Mn2O7 double perovskite produced by the sol-gel wet chemical method was investigated. XRD analysis reveals that all samples have different percentages of tetragonal I4/mmm space group (double perovskite) and orthorhombic Pnma (perovskite) space group with. All samples showed a ferromagnetic to paramagnetic transition and a systematic decrease in T-C values was observed from 250 K for x = 0.0 to 150 K for x = 0.4 sample due to the increased amount of K+ due to the coexistence of different ferromagnetic and antiferromagnetic interaction ratios in the samples. A decrease in the magnetic entropy change values was also observed with the decrease in the ferromagnetic double exchange interaction, due to the fact that the Mn4+ ions increasing with the K+ doping support the antiferromagnetic Mn4+-O2--Mn4+ super-exchange interactions. For the field change of 1 T, the maximum magnetic entropy change for the sample La1.4Ca1.6Mn2O7 was found to be 1.0 Jkg(-1) K-1 it decreased down to 0.68, 0.75 and 0.60 Jkg(-1) K-1 for La1.3K0.1Ca1.6Mn2O7, La1.2K0.2Ca1.6Mn2O7, La1.0K0.4Ca1.6Mn2O7, respectively. Experimental results indicate that the samples can be potential candidates for sub-room temperature magnetic cooling application.