Comparison of structural, magnetic and electrical transport behavior in bulk and nanocrystalline Nd-lacunar Nd0.67Sr0.33MnO3 manganites

Observation of enhanced magnetic entropy change near room temperature in Sr-site deficient La0.67Sr0.33MnO3 manganite

“…37 On the other hand, La-0.09 and Sr-0.09 compounds show an additional peak at 36.1 due to the presence of Mn 3 O 4 as a secondary phase as reported in our previous work. 37,48,49 However, in the present case, Sr-0. 18 compounds.…”

“…The increase in unit cell volume of Sr-site decient compounds can be related to the decreasing concentration of oxygen due to the formation of anionic vacancies and the increase in radius of the decient Srsite. 37,48,49,59 The presence of oxygen vacancies is compensated by a reduction in the average valence of manganese ions. This leads to the reduction of some Mn 4+ to Mn 3+ and Mn 3+ to Mn 2+ .…”

“…[28][29][30][31][32][33][34][35][36][37] Recently, many reports have demonstrated that the creation of deciency at the rare Earth and alkaline rare Earth sites alter the Mn 2+ /Mn 3+ /Mn 4+ ratio which severely affect the magnetic and magnetocaloric properties. [37][38][39][40][41][42][43][44][45][46][47][48][49] The structure of manganites is imperfect and contain vacancy type point defects, called Schottky defects due to the cyclic temperature changes during synthesis and sintering process. 50,51 The presence of cation (V (c) ) and anion (V (a) ) vacancies strongly inuence the properties of the manganites and causing a change in the stability of the perovskite structure.…”

“…The Jahn-Teller active ion, Mn 3+ distorts the MnO 6 octahedra due to the strong Jahn-Teller effect, while Mn 2+ and Mn 4+ are Jahn-Teller inactive and do not tend to distort the octahedrally coordinated system. The iodometric titration method was performed to estimate the oxidation state of manganese and hence the stoichiometry of the oxygen ion 48,61. Powders of Sr-decient compounds are weighed and dissolved in a mixture of 10 ml of 10 mass% KI aqueous solution and 2.5 ml of 2 M HCl.…”

Magnetocaloric effect and critical behavior near the first to second-order phase transition of La0.7Ca0.3−xSnxMnO3 compounds

“…It is known that the hole doped perovskite manganite La 0.7 Ca 0.3 MnO 3 is a typical material exhibiting a colossal magnetoresistance (CMR) and a magnetocaloric effect (MCE) with high values magnetoresistance (MR) and magnetic entropy change (ΔS m ), respectively. These values are almost larger than those obtained on the other manganites [1][2][3][4][5][6][7]. Nevertheless, La 0.7 Ca 0.3 MnO 3 polycrystalline or single crystal bulk sample is a first-order phase transition (FOPT) material [8][9][10][11].…”