Synthesis, structure, morphology, magnetism, and magnetocaloric-effect studies of (La1−xPrx)0.7Sr0.3MnO3 nanocrystalline perovskites

Abstract

Single-Phase (La1–xPrx)0.7Sr0.3MnO3 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) perovskites were synthesized by the sol–gel method followed by sintering at 700 °C for 5 h. Samples with x = 0.0–0.4 are found to crystallize into rhombohedral structure (R-3c space group) while the ones with x = 0.6–1.0 crystallize into orthorhombic structure (Pbnm space group). The average particle size of the samples was in the range of 21–44 nm. All samples exhibit a ferromagnetic to paramagnetic second-order magnetic phase transition at Curie temperature, which is found to decrease linearly with increasing the Pr concentration. The magnetic coercivity was found to be small (~ 10 Oe) for all the samples, at T < TC. The experimental effective paramagnetic moment (µeff) is found to increase with increasing x from 3.99 µB (x = 0.0) to 5.05 µB (x = 1.0). The magnitude of the maximum magnetic entropy change (−ΔSM)max. and the relative cooling power (RCP) for the samples having orthorhombic structure increases as x increases reaching a maximum value of 4.67 J/kg.K and 574 J/kg at ΔµoH = 9 T for x = 1.0. While the ones with the rhombohedral structure have the maximum values of (−ΔSM)max. and RCP of 4.63 J/kg.K and 472 J/kg at ΔµoH = 9 T are for x = 0.2. The large values of (−ΔSM)max. and RCP (at room temperature (RT)) and the wider temperature range of −ΔSM for the sample with x = 0.6 suggests that this compound may be considered as magnetic refrigerant material at RT, and the other compounds can be candidates in the vicinity of RT.

Investigation of the impact of A-site cation disorder on the structure, magnetic properties, and magnetic entropy change of trisubstituted divalent ions in La0.7(Ba,Ca,Sr)0.3MnO3 manganite

“…49 The spin-orbit splitting of the La 3d level (B16.8 eV) was identical for all the compounds and was close to those observed for perovskite samples. [48][49][50][51] The Ba 3d core levels exhibit doublet structures, as shown in Fig. 8c.…”

“…The difference in the binding energy is B11.7 eV, which is close to those observed for perovskite samples. 50 Based on stoichiometry, LBCS compounds have mixed valence Mn 3+ and Mn 4+ , which appear due to the divalent substitution at the A-site. Previous studies indicated that the binding energies near Mn 2p 3/2 for Mn 2 O 3 (641.7 eV) and MnO 2 (642.8 eV) correspond to these specific manganese oxides Mn 3+ and Mn 4+ , respectively.…”

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

“…Both represent the amount of heat available for transfer between the hot and cold sides in one ideal Carnot cycle. 39,47,48…”

“…1 Furthermore, many researchers have assumed that δ T FWHM = T 2 − T 1 , where T 2 and T 1 are the normalizations of the value . 47,49…”

“…Many researchers have reported two types of magnetic phase transition orders based on the results of these curves. 1,4,7,16,17,41,47,48,52–57 If the first derivative results in a discontinuous curve marked by a magnetic phase transition at critical points within a very narrow temperature range, such as changes in entropy, volume, and magnetization values, it is known as the behavior of a first-order magnetic phase transition (FOMT). 54,55,57 This phenomenon often occurs when the magnetic transition (dis)order–order occurs parallel to changes in the underlying crystal lattice, which is associated with magnetostructural transformations accompanied by the emergence of hysteresis.…”