Mn substitution effect on the local structure of La(Fe1- xMnx)AsO studied by temperature dependent x-ray absorption measurements

M Y Hacisalihoglu; L Simonelli; C Marini; A Provino; A Martinelli; P Manfrinetti; M Putti; N L Saini

doi:10.1088/1361-648X/abcdb3

Mn substitution effect on the local structure of La(Fe_{1- x}Mn_x)AsO studied by temperature dependent x-ray absorption measurements

J Phys Condens Matter. 2020 Dec 16;33(9). doi: 10.1088/1361-648X/abcdb3.

Authors

M Y Hacisalihoglu^{1

2}, L Simonelli³, C Marini³, A Provino^{4

5}, A Martinelli⁴, P Manfrinetti^{4

5}, M Putti^{4

6}, N L Saini¹

Affiliations

¹ Dipartimento di Fisica, Università di Roma 'La Sapienza', P. le Aldo Moro 2, 00185 Roma, Italy.
² Department of Physics, Recep Tayyip Erdogan University, 53100 Rize, Turkey.
³ CELLS-ALBA Synchrotron Radiation Facility, Carrer de la Llum 2-26, 08290, Cerdanyola del Valles, Barcelona, Spain.
⁴ CNR-SPIN, Corso Perrone 24, I-16152 Genoa, Italy.
⁵ Department of Chemistry, University of Genova, via Dodecaneso 31, I-16146 Genova, Italy.
⁶ Department of Physics, Sapienza University of Rome, P. le Aldo Moro 2, 00185 Roma, Italy.

PMID: 33331297
DOI: 10.1088/1361-648X/abcdb3

Abstract

The local structure of La(Fe_1-xMn_x)AsO has been investigated using temperature dependent Fe K-edge extended x-ray absorption fine structure (EXAFS) measurements. The EXAFS data reveal distinct behavior of Fe-As and Fe-Fe atomic displacements with a clear boundary betweenx⩽ 0.02 andx> 0.02. The Fe-As bondlength shows a gradual thermal expansion while the Fe-Fe bond manifests a temperature dependent anomaly at ∼180 K forx> 0.02. It is interesting to find characteristically different nature of Fe-As and Fe-Fe bondlengths shown by the temperature dependent mean square relative displacements. Indeed, the Fe-As bond, stiffer than that of the Fe-Fe, gets softer forx⩽ 0.02 and hardly shows any change forx> 0.02. On the other hand, Fe-Fe bond tends to be stiffer forx⩽ 0.02 followed by a substantial softening forx> 0.02. Such a distinction has been seen also in the As K-edge x-ray absorption near edge structure, probing local geometry around As atom together with the valence electronic structure. The results suggest that local atomic displacements by Mn substitution inducing increased iron local magnetic moment that should be the main reason for its dramatic effect in iron-based superconductors.

Keywords: Mn substitution effect; iron pnictides; local structure; superconductivity.