Synthesis, characterisation and study of magnetocaloric effects (enhanced and reduced) in manganate perovskites

Abstract

Highlights• La1-xCaxMnO3 and La1-xBaxMnO3 synthesised using the modified peroxide sol-gel synthesis.• Enhanced magnetic heating for manganates doped with A-site cations larger than La 3+ .• Reduced magnetic heating observed for manganates doped with A-site cations smaller than La 3+ . 1 AbstractThe effect of the A-site dopant ionic radii on the observed magnetocaloric effect (MCE) exhibited by three different families of manganese-based perovskites was investigated using both induction heating and SQUID magnetometry measurements. The doped perovskites La1-xSrxMnO3 (LSMO), La1-xCaxMnO3 (LCMO), and La1-xBaxMnO3 (LBMO) (x = 0.25, 0.35, 0.4) were prepared using a modified peroxide sol-gel synthesis. This method has not been previously used for the synthesis of LCMO or LBMO. Structural characterisation of the agglomerates of magnetic nanoparticles (MNP) for each material was carried out using SEM, XRD and IR spectroscopy. Magnetic heating was observed for materials with larger A-site dopant radii relative to La 3+ ; LSMO40 and LBMO40, with average SARs obtained of 51.5 Wg -1 Mn and 33.8Wg -1 Mn respectively. However, reduced magnetic heating effects were observed for smaller A-site dopant radii relative to La 3+ (LCMO). In fact, the calculated Specific Absorption Rate for LCMO40 of 14.72 Wg -1 Mn is half that of the blank.

Improving the crystallinity and magnetocaloric effect of the perovskite La0.65Sr0.35MnO3 using microwave irradiation

“…For example, in the calculation of crystallite diameter from the un-refined diffraction pattern of La0.6Sr0.4MnO3 the average crystallite size is 61.9 nm 32 , whereas calculating this following Rietveld refinement gives orthorhombic and rhombohedral crystallite diameters of 16.5 and 37.4 nm respectively. 57 The crystallite diameters have been calculated for the data post-Rietveld refinement and are shown in Table 2, however the average crystallite size was calculated on the data pre-Rietveld refinement in order to calculate the magnetically dead layer in Section 3.2.…”

Analysis Crystal Structure of La0.7Ba(1-xSrx)0.3MnO3 by Sol-Gel Method

“…This structure can be modified through doping of divalent ion at La-site and transition ion at Mn-site. Substituted La-site with divalent ion such as Ba, Sr, and Ca can change Mn content from Mn 3+ to Mn 4+ , this phenomena can be explain with double exchange (DE) effect [1][2], a system by which electron mobility between the nearest Mn ions, preferably, those with aligned spins is preferred [3].…”

Temperature-dependent structural and magnetic properties of R2MMnO6 double perovskites (R = Dy, Gd; M = Ni, Co)

“…In recent years, rare earth double perovskites R 2 MMnO 6 (M being Ni or Co) have attracted widespread attention due to their rich physical properties, showing a complicated interplay between electric and magnetic properties [1][2][3][4][5][6][7][8][9][10][28][29][30][31]. However, in contrast to the extensively investigated La 2 CoMnO 6 compound, less consideration has been given to other perovskite manganites such as R 2 MMnO 6 (R = Dy and Gd) [32][33][34][35][36][37][38].…”