Abstract
The aim of the work was to check how the introduction of alkali and cobalt ions into a manganese structure can affect the structural disorder and, in consequence, lead to the changes (improvements) of magnetic properties. The high-pressure sintering technique was applied to check if the external factor can modify the magnetization of manganites. Nanocrystalline La0.9A0.1Mn0.9Co0.1O3 (where A is Li, K, Na) powders were synthesized by the combustion technique. The respective powders were used for nanoceramics preparation by the high-pressure sintering technique. The structure and morphology of the compounds were studied by X-ray powder diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Magnetization studies for all compounds were performed in order to check the changes induced by either codoping or the sintering pressure. It was found that the type of the dopant ion and sintering pressure produced significant changes to the magnetic properties of the studied compounds. Alkali ions lead to the stabilization of Co ions in the +2 oxidation state and the formation of positive exchange interactions Mn3+–Mn4+ and Co2+–Mn4+ and the subsequent increase in remanent magnetization. High sintering pressure leads to a decrease in grain size and reduction of long-range ferromagnetic order and lower magnetization.
Highlights
IntroductionMultiferroics are compounds which in one phase exhibit more than one primary ferroic order (ferromagnetism, ferroelectricity or ferroelasticity) [1]; in recent years this term has beenAppl
Multiferroics are compounds which in one phase exhibit more than one primary ferroic order [1]; in recent years this term has beenAppl
The analysis of the X-ray diffraction (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 La0.9 A0.1 MnO3 compounds, previously studied by the authors [24], and other
Summary
Multiferroics are compounds which in one phase exhibit more than one primary ferroic order (ferromagnetism, ferroelectricity or ferroelasticity) [1]; in recent years this term has beenAppl. Sci. 2020, 10, 8786 mainly used for magnetoelectric materials. Such materials have both magnetic and ferroelectric properties simultaneously. To obtain magnetic materials where magnetic moments are not cancelled out by each other, it is necessary to exclude all ions where outer orbitals are completely filled. This limits the potential multiferroic materials to systems containing either transition metals with partially filled 3d shells or lanthanides with partially filled 4f shells. In the case of ferroelectricity, the Jahn–Teller effect has to be taken into account [2], where oppositely charged ions form a local dipole with a spatially degenerate electronic ground state. For the purpose of removing this degeneracy in the structure, a geometrical distortion appears to lead to the lowering of the overall energy of the system
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
