Department of Physics
Library of the School of Science

2021-08-09

2021

Georgalas Konstantine

Λελίδης Ιωάννης, Αναπλ. Καθηγητής (κύριος επιβλέποντας), Σχολή Θετικών Επιστημών, Τμήμα Φυσικής, Ε.Κ.Π.Α.
Σταμόπουλος Δημοσθένης, Αναπλ. Καθηγητής, Σχολή Θετικών Επιστημών, Τμήμα Φυσικής, Ε.Κ.Π.Α.
Στεφάνου Νικόλαος, Καθηγητής,Σχολή Θετικών Επιστημών, Τμήμα Φυσικής, Ε.Κ.Π.Α.
Ράπτης Ιωάννης, Καθηγητής, Σ.Ε.Μ.Φ.Ε., Ε.Μ.Π.
Τσεκούρας Αθανάσιος, Επίκουρος Καθηγητής, Τμήμα Χημείας, Ε.Κ.Π.Α.
Πίσσας Μιχαήλ, Ερευνητής Α΄ του Ινστιτούτου Νανοεπιστήμης και Νανοτεχνολογίας του ΕΚΕΦΕ Δημόκριτος Μεργιά Κωνσταντίνα, Διευθύντρια Ερευνών του Ινστιτούτου Πυρηνικών και Ραδιολογικών Επιστημών και Τεχνολογίας, Ενέργειας και Ασφάλειας του ΕΚΕΦΕ Δημόκριτος.

Επίδραση του Μεγέθους και της Στοιχειομετρίας των Ιόντων στην Τροχιακή και τη Μαγνητική Τάξη σε Ενώσεις Τύπου Περοβσκίτη του Mn

Greek

The effect of Size and Stoichiometry of Ions on the Orbital and Magnetic Ordering in Manganese Perovskites

In manganese perovskites, the Colossal Magnetoresistance (CMR) phenomenon includes a complex coupling among charge, orbital and spin freedom degrees of manganese magnetic ions. The powerful interplay between electron and phonon and its correlation with the dynamic Jahn-Teller (J-T) lattice distortions could contribute to the microscopic interpretation on the CMR phenomenon. Manganese perovskites of the type LaMn1-xBxO3 (B: transition metal as well as other metalloid element) seem to be ideal systems for studying the close relationship, governing the cooperative J-T lattice deformation, the magnetic interactions of Double-Exchange (DE) / Super-Exchange (SE) and the orbital degeneration.
In the present work, a thermodynamic study of the J-T transition (depending on the electron-phonon coupling) in LaMn1-xBxO3 compounds is carried out for the first time. The nature of indirect SE or DE interactions among Mn3+, Mn4+, Cr3+, Fe3+ and Ga3+ ions is also investigated. The aim of the present work is to reveal the strong correlation between orbital and magnetic ordering in LaMn1-xCrxO3, LaMn1-xFexO3, LaMn1-xGaxO3 and LaMn1-xCrxO3+δ compounds, affected by the change of average ionic radius at B-site, and the non-stoichiometry factor of oxygen, δ.
It is concluded that the correlations of the local J-T lattice distortions are completely weakened at lower concentrations of impurities, x, while the establishment both isotropic SE-FM Mn3+-Mn3+ interactions and «Pseudocubic» phase is taking place at higher concentrations. The weakening of the cooperative J-T deformation seems to be affected not only by the change of the , but also by the nature of spin interactions among Cr3+, Fe3+, Ga3+ and Mn3+ ions. The results probably show that the magnetic interaction between Mn3+-Cr3+ is not DE. In general, the strong coupling of orbital and magnetic ordering in these compounds is highlighted.

Science

Manganites, Orbital order, Jahn-Teller transition, Specific heat, Ferromagnetism, Superexchange interactions

Yes

5

Yes

183

207

File access is restricted until 2024-08-10.

https://pergamos.lib.uoa.gr/uoa/dl/object/2959538