Vibrational abisotropy and quadrupole interactions of Fe substituted into Mn site of the charge and orbitally ordered and disordered layered manganites LnBaMn1.96Fe0.04O5 and LnBaMn1.96Fe0.04O6 (Ln=Y,Gd,Sm,La)

TL;DR

This study investigates the vibrational anisotropy and quadrupole interactions in Fe-doped layered manganites using x-ray diffraction and Mössbauer spectroscopy, revealing effects of texture and charge-orbital order on local electronic environments.

Contribution

It provides new insights into the interplay of vibrational anisotropy, preferred orientation, and charge-orbital order in Fe-substituted manganites through combined diffraction and spectroscopic analysis.

Findings

Vzz axis aligned perpendicular to layers with different signs in oxygen-rich and oxygen-poor series.

Constructive and destructive interference effects between texture and vibrational anisotropy observed.

Charge-orbital order melting around Fe dopants explains single-site spectra in most samples.

Abstract

A-site ordered manganites LnBaMn1.96Fe0.04O5 and LnBaMn1.96Fe0.04O6 are investigated by x-ray full-profile diffraction and Moessbauer spectroscopy. Powder samples were oriented with preferred orientation of platy crystallites in the plane of sample surface. March-Dollase function of preferred orientation was employed in analysing both the Rietveld patterns and the Mossbauer spectra. Combined effects of preffered orientation and vibrational anisotropy on the line area asymmetry of Mossbauer doublet are analysed. Constructive and destructive interference between the effects of texture and vibrational anisotropy is observed in LnBaMn1.96Fe0.04O6 and LnBaMn1.96Fe0.04O5, respectively. Both series of the manganites show the main axis of electric field gradient perpendicular to layers (Vzz along c) with Vzz>0 in oxygen-poor series and Vzz<0 in oxygen-rich series. Charge-orbital order (COO) melting around Fe dopants explains the single-site spectra observed for several Ln in both "O5" and "O6" series, except LaBaMn1.96Fe0.04O5. However, the short-range COO persists to be observed in magnetization and in Rietveld patterns.