Abstract
The changes of structural, magnetic and electrical parameters of ceramic La0.8-xSr0.2+xMn1-xTixO3+γ (0.025 ≤ x ≤ 0.150) manganites during long-term storage at room temperature and after thermal cycling were investigated. The unit cell volume (V) of all manganites decreased over time. Most considerable decrease of V and broadening of X-ray diffraction lines width were observed in the samples with high quantity of titanium. During the storage period magnetization (σ) and Curie point (Tc) of manganites with relatively low Ti content decreased, while the compositions with high values of “x” exhibited some trend of σ and Tc increase. The resistance of the samples with x < 0.100 increased over time. Fluctuations of magnetization of all thermal-aged samples were within the error of measurement, and Curie point of manganites with x = 0.150 showed the rise. From the data obtained it might be inferred that ageing phenomena in Ti-substituted manganites can be associated with oxidation processes, the transfer of Ti4+ to vacant sites in rare-earth sublattice and formation of microinhomogeneities.
Highlights
The development of new perspective materials for magnetoelectronics and spintronics, such as ferrites, manganites exhibiting colossal magnetoresistance or manganite electroceramics for thermistors, involves the achieving a number of valuable properties, among which stability of functional parameters in relation to thermal and prolonged storage ageing is of special importance [1,2,3]
- resistance of the samples with x 0.100 increased and with x ≥ 0.100 decreased during storage period;
- at low titanium content all X-ray reflexes narrowed over time and at high content they broadened;
Summary
The development of new perspective materials for magnetoelectronics and spintronics, such as ferrites, manganites exhibiting colossal magnetoresistance or manganite electroceramics for thermistors, involves the achieving a number of valuable properties, among which stability of functional parameters in relation to thermal and prolonged storage ageing is of special importance [1,2,3]. We present the experimental investigations on the in-time and thermal ageing of Ti-substituted manganites of designed system La3+0.8–xSr2+0.2+xMn3+0.8–x–2γMn4+0.2+2γTi4+xO3+γ (0.025 ≤ x ≤ 0.150), in which Mn4+ content is independent of "x". These manganites under synthesis conditions in our experiments have excess oxygen content ( > 0) [9,10,11], and after cooling they are not in a state of thermodynamic equilibrium. The transition into energetically more favorable state is a general cause of the ageing processes
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