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

Abstract

The 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 La3+; LSMO40 and LBMO40, with average SARs obtained of 51.5Wg−1Mn and 33.8Wg−1Mn respectively. However, reduced magnetic heating effects were observed for smaller A-site dopant radii relative to La3+ (LCMO). In fact, the calculated Specific Absorption Rate for LCMO40 of 14.72Wg−1Mn is half that of the blank.