Abstract
Nanocrystalline La0.9A0.1MnO3 (where A is Li, Na, K) powders were synthesized by a combustion method. The powders used to prepare nanoceramics were fabricated via a high-temperature sintering method. The structure and morphology of all compounds were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). It was found that the size of the crystallites depended on the type of alkali ions used. The high-pressure sintering method kept the nanosized character of the grains in the ceramics, which had a significant impact on their physical properties. Magnetization studies were performed for both powder and ceramic samples in order to check the impact of the alkali ion dopants as well as the sintering pressure on the magnetization of the compounds. It was found that, by using different dopants, it was possible to strongly change the magnetic characteristics of the manganites.
Highlights
The discovery of the colossal magnetoresistance (CMR) effect in alkaline ion (A)-doped rare earth (RE) perovskite-type manganites with a composition of RE1−x Ax MnO3, has attracted ample attention in recent years [1,2,3]
The La0.9A0.1MnO3 powders and ceramics were characterized by X-ray diffraction performed at room temperature (Figure 1)
Rietveld refinement using X’pert HighScore Plus software. This procedure revealed that the crystal structure of the manganite nanoparticles was rhombohedral with an R-3c space group
Summary
The discovery of the colossal magnetoresistance (CMR) effect in alkaline ion (A)-doped rare earth (RE) perovskite-type manganites with a composition of RE1−x Ax MnO3 , has attracted ample attention in recent years [1,2,3]. The studies on such manganites have revealed that the CMR effect is attributed to the presence of Mn3+ and Mn4+ ions together with the site–site double-exchange (DE). The DE mechanism links the electronic properties to the magnetic transition and describes the hopping of electrons in eg orbitals between neighboring Mn3+ and Mn4+ ions with strong on-site Hund’s coupling by an O2− anion. As the CMR effect is often attributed to the Jahn–Teller (JT) effect [11], a parent compound of several important mixed-valence
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