Structure, phase transitions, 55 Mn NMR, magnetic and magnetotransport properties of the magnetoresistance La 0.9−x Ag x Mn 1.1 O 3−δ ceramics

Spin-dependent magnetism and superparamagnetic contribution to the magnetocaloric effect of non-stoichiometric manganite nanoparticles

“…According to the established defect formation mechanism for real perovskite structure with point defects of vacancy type (cation V (c) and anion V (a) vacancies) [26,49,50], the overstoichiometric manganese can occupy the cation deficient A-and B-sites in form of 2 Mn A  and 34 Mn / Mn BB  ions, respectively. The appearance of Mn 2+ ions was observed earlier for similar A-cation deficient manganites [17,18,20,21] and will be proved below using (X-ray photoelectron spectroscopy) XPS method.…”

Expansion of the multifunctionality in off-stoichiometric manganites using post-annealing and high pressure: physical and electrochemical studies

“…This work presents the results of a parallel study of the electrochemical properties of La 0.9 Mn 1.1 O 3 manganites along with investigating changes in crystallite sizes, structural features, and thermal properties, as well as their interconnection. For this purpose, off-stoichiometric La 0.9 Mn 1.1 O 3Àd ceramic samples have been selected and synthesized due to the following reasons: (i) high reproducibility of the samples, 3,32,38 (ii) Mn-containing perovskites are effective catalysts, 18 (iii) this offstoichiometric compound 0.9 : 1.1 : 3Àd demonstrates the nonzero magnetization in contrast to the classical antiferromagnetic (AFM) one 1 : 1 : 3, 41 (iv) they have one of the most stable perovskite crystal structure with a tolerance factor t of 0.946 closed to 1, 42 (v) the presence of cation vacancies at A-positions leads to the appearance of an additional magnetism from Mn 2+ ions, 2,23,[25][26][27][28] and (vi) the overstoichiometric manganese on B-sites improves the magneto-transport and magnetocaloric properties. 3,[33][34][35][36]40 Thus, the structural, microstructural, magnetic, magnetocaloric, and electrochemical properties of La 0.9 Mn 1.1 O 3 ceramics depending on post-annealing and/or high hydrostatic pressure have been studied systematically.…”

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

“…[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. 52 The change in the valence state and coordination number of cations due to defect formation affects the magnetic phase transition temperature and magnetic ordering of the manganites.…”

“…The interstitial point defects, called Frenkel defects is not formed in these compounds and only vacancy type point defects are exist due to elevated synthesis and sintering temperature conditions. 50 The anion vacancies are formed during heating process due to the thermal dissociation of oxygen and that leads to the reduction of oxygen content to O 3− δ . 51 Moreover, the presence of vacancies at the oxygen site is compensated by a reduction in the average valence of manganese ions.…”