Role of Potassium Substitution in the Magnetic Properties and Magnetocaloric Effect in La0.8−xKxBa0.05Sr0.15MnO3 (0 ≤ x ≤ 0.20)

Abstract

The magnetic and magnetocaloric effects of potassium-substituted La0.8−xKxBa0.05Sr0.15MnO3 (0 ≤ x ≤ 0.20) manganite were explored. The samples in polycrystalline form were synthesized by the sol–gel method, with a final sintering temperature of 1100 °C. Powder X-ray diffraction (XRD) patterns refined by Rietveld refinement show that all samples crystallized in rhombohedral structure with R-3c space group. The unit cell volume of the samples decreases with increasing potassium concentration. In addition, small changes in average bond length and bond angle are also observed in the samples. Scanning electron microscope (SEM) images reveal that the largest average grain size was observed for x = 0.10. Field-cooled (FC) magnetization measurements show that the Curie temperature ( T C ) of the samples increases from 320 K for x = 0 to 360 K for x = 0.2. The largest magnetocaloric (MCE) effect, which is represented by maximum magnetic entropy change (− Δ S M , M A X ), reaches its greatest value for the x = 0.10 sample. The monotonous increase in T C suggests that TC is mainly governed by the ferromagnetic coupling between Mn ions induced by the changes on average bond length and bond angle. The obtained − Δ S M , M A X value suggests that MCE property is more sensitive to Zener theory of double exchange, which is strongly related to the Mn3+/Mn4+ ratio of the samples.

The magnetocaloric effect properties for potential applications of magnetic refrigerator technology: a review

“…To estimate its size, a formulation has been proposed as defined below. 17 〈 r A 〉 = Σ x i r i where, 〈 r A 〉 is the average ion radius size, x i is the ion content in the system, and r i is the ion radius size in the system. Fig.…”

“…48 Additionally, Razaq et al reported that La 0.8 K 0.1 Ba 0.05 Sr 0.15 MnO 3 has a t value of 0.965, displaying a rhombohedral structures. 17…”

“…The main challenge in the expensive development of MRT is the use of Gd as a material, which has a high ($4000 per kg), and limited availability. 17 Therefore, there is a need for alternative materials that are more affordable and abundantly available in nature.…”

Viable Materials with a Giant Magnetocaloric Effect

“…; Tm in TmZn [198] and metallic glasses [233]; rare earth in clathrates [277,296], etc. Manganites [258] include La 0.7 Ca 0.3 MnO 3 [227,262,264,285], La 0.48 Ca 0.52 MnO 3 [174], Na-deficient La 0.8 Na 0.2−x MnO 3 [185], La 0.67 Sr 0.16 Ca 0.17 MnO 3 [207], La 0.8−x K x Ba 0.05 Sr 0.15 MnO 3 [297], as well as containing critical rare earth La 0.7−x Pr x Ca 0.3 MnO 3 [160], GdMnO 3 [186], Gd 2 NiMnO 6 and Gd 2 CoMnO 6 [193], TbMnO 3 [165,252], DyMnO 3 [247], PrPb manganites [294], etc. Materials containing highly toxic arsenic include MnAs [123,131,210,238,245,246,256,265,273,276,282,289] and MnFe(P,As) [48,49,239,298].…”

Regulating the Electron Transport Mechanism and Increasing Magnetoresistance: The Role of CuO Filler in La0.7Sr0.2Ca0.1MnO3 Grain Boundary

“…The CMR effect in perovskite rare earth manganates can lead to significant changes in the electrical resistivity of these materials in response to magnetic fields. The double exchange mechanism, first introduced by Zener in 1951 [19], is the underlying mechanism that causes this effect. The CMR effect can be classified into two categories: intrinsic CMR and extrinsic CMR.…”