Effects of A -site ordering on the Mn local structure and polar phases of R Ba Mn 2 O 6 ( R = La , Nd, Sm, and Y)

Subías, G. ; Blasco, J. (Universidad de Zaragoza) ; Cuartero, V. (Universidad de Zaragoza) ; Lafuerza, S. ; Simonelli, L. ; Gorni, G. ; Castro, M. (Universidad de Zaragoza) ; García, J.

Resumen: We have investigated the temperature dependence of the Mn local structure in A-site ordered RBaMn2O6 (R = La, Nd, Sm, and Y) perovskites, in parallel with their disordered counterparts, R0.5Ba0.5MnO3, by means of x-ray emission (XES) and x-ray absorption spectroscopy (XAS) The end member LaBaMn2O6 shows a nearly regular MnO6 octahedron independent of temperature. With decreasing the R ionic radius in the ordered samples, the XAS results indicate that a local distortion develops in the MnO6 octahedron at the low-temperature charge-localized and polar phases. For NdBaMn2O6, this local distortion is tiny, indicating the absence of charge segregation at the Mn site. This is followed by a bigger local distortion anticipated for SmBaMn2O6 in its respective charge-localized and polar phase and finally, the biggest local distortion for the smallest A-site cation ordered compound, YBaMn2O6, for which it even persists above the polar charge-localization transition temperatures. The high-resolution XAS spectra confirm the presence of charge segregation between two nonequivalent Mn sites in the low-temperature polar phase of Sm and Y ordered samples. Thus, our XAS study suggests a displacive mechanism for the charge-localization and polar transitions in the Nd and Sm ordered samples while a combination of displacive and order-disorder contributions is revealed for YBaMn2O6. Besides, calorimetric measurements confirm the combination of the two mechanisms, order-disorder and displacive, for the ordered Sm and Y compounds. On the other hand, the A-site disordered R0.5Ba0.5MnO3 samples with R cations smaller than Nd present a significant static (temperature-independent) local disorder, which explains why
polar charge-localization transitions are not developed in these samples. Finally, we correlate our results about the Mn local structure and character of the transitions with the macroscopic magnetic and electric behavior of both A-site ordered and disordered compounds.

Idioma: Inglés

DOI: 10.1103/PhysRevB.107.165133

Año: 2023

Publicado en: Physical Review B 107, 16 (2023), 165133 [13 pp.]
ISSN: 2469-9950

Factor impacto JCR: 3.2 (2023)

Categ. JCR: MATERIALS SCIENCE, MULTIDISCIPLINARY rank: 201 / 438 = 0.459 (2023) - Q2 - T2
Categ. JCR: PHYSICS, CONDENSED MATTER rank: 31 / 79 = 0.392 (2023) - Q2 - T2
Categ. JCR: PHYSICS, APPLIED rank: 62 / 179 = 0.346 (2023) - Q2 - T2

Factor impacto SCIMAGO: 1.345 - Electronic, Optical and Magnetic Materials (Q1) - Condensed Matter Physics (Q1)

Financiación: info:eu-repo/grantAgreement/ES/MCIU-FEDER/RTI2018-098537-B-C22
Financiación: info:eu-repo/grantAgreement/ES/MICINN/PID2021-124734OB-C21

Tipo y forma: Article (Published version)

Área (Departamento): Área Mecánica de Fluidos (Dpto. Ciencia Tecnol.Mater.Fl.)
Área (Departamento): Área Cienc.Mater. Ingen.Metal. (Dpto. Ciencia Tecnol.Mater.Fl.)