Magnetic Properties of La0.9A0.1MnO3 (A: Li, Na, K) Nanopowders and Nanoceramics

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.

Impact of Alkali Ions Codoping on Magnetic Properties of La0.9A0.1Mn0.9Co0.1O3 (A: Li, K, Na) Powders and Ceramics

“…This procedure allowed to attest the phase purity of the compounds and also to determine the crystal structure and structural parameters. The analysis of the XRD results indicated the rhombohedral symmetry described by R-3c space group (ICSD 75070) [28], which are similar to the structural results obtained for the La 0.9 A 0.1 MnO 3 compounds, previously studied by the authors [24], and other LaMnO 3 -based compounds [29]. It should be noted that the crystal structure of undoped compounds is also characterized by the rhombohedral distortion of the unit cell which implies nominal oxygen excess in LaMnO 3+δ (δ > 1%) compounds [30], leading to nonzero remanent magnetization as compared to stoichiometric LaMnO 3 having an orthorhombic structure [31].…”

“…Chemical substitution with alkali elements and cobalt ions leads to an increase in the magnetization of the compounds which is caused by the higher number of manganese ions having +4 oxidation state and thus leading to the strengthening of positive exchange interactions Mn 3+ -Mn 4+ . Certain deviations from the above mentioned tendency were ascribed to the modification in the oxidation during the synthesis process [24] and thus to variations in the exchange interactions formed between Co and Mn ions.…”

“…The complex magnetic structure of the initial LaMnO 3 compound is associated with a lack in the cation content and thus the nominal excess of oxygen content leading to the formation of competing positive (Mn 3+ -O-Mn 4+ ) and negative (Mn 3+ -O-Mn 3+ ; Mn 4+ -O-Mn 4+ ) exchange interactions associated with ferromagnetic and antiferromagnetic orders, respectively. The competing antiferromagnetic and ferromagnetic phases lead to the formation of a mixed magnetic state, which is characteristic for LnMnO 3 -based systems [24,[42][43][44][45]. Chemical substitution with alkali elements and cobalt ions leads to an increase in the magnetization of the compounds which is caused by the higher number of manganese ions having +4 oxidation state and thus leading to the strengthening of positive exchange interactions Mn 3+ -Mn 4+ .…”

“…This work proposes a new approach to changing the magnetic properties of one of the types of manganites by introducing aliovalent ions and applying pressure. The paper is a continuation of our work on changing the magnetic properties of manganites by doping their structure with alkaline metal ions [24].…”

The Effects of La Doping on the Crystal Structure and Magnetic Properties of Ni2In-Type MnCoGe1−xLax (x = 0, 0.01, 0.03) Alloys

“…Pr, Nd, Tb, and Dy resources are scarce, while La and Ce resources are abundant and overstocked. Therefore, in recent years, the development of magnetic materials containing La and Ce has become the focus of attention in academia and industrial production [ 22 , 23 , 24 , 25 ].…”