A hard X- ray probe to study doping-dependent electron redistribution and strong covalency in La_{1-x}Sr_{1+x}MnO_4

TL;DR

This study uses hard X-ray emission spectroscopy to investigate how doping affects electron distribution and covalency in La_{1-x}Sr_{1+x}MnO_4, revealing minimal changes at Mn sites and significant charge redistribution involving oxygen.

Contribution

It provides new insights into doping effects on electronic structure and covalency in La_{1-x}Sr_{1+x}MnO_4 using non-resonant hard X-ray emission spectroscopy and theoretical calculations.

Findings

Dichroism in Mn K-beta lines decreases with doping

Mn charge and spin density are minimally affected by doping

Holes mainly reduce charge density on oxygen atoms

Abstract

The effect of doping on the electronic structure at the Mn sites in the La_{1-x}Sr_{1+x}MnO_4 series (x=0, 0.3 and 0.5) was studied by means of non-resonant hard X- ray emission spectroscopy (XES). We observe a linear dichroism in the Mn K-beta main lines (3p to 1s transitions) that is strongest for x=0 and decreases with increasing x to 0.5. The Mn K-beta main lines in the poly-crystalline samples change considerably less upon increasing the hole doping (substitution of La by Sr) than it would be expected based on the change of formal valence. From this we conclude that the charge and spin density at the Mn sites are only little affected by doping. This implies that holes injected in the La_{1-x}Sr_{1+x}MnO_4 series mainly result in a decrease of charge density on the oxygen atoms, i.e. oxygen takes part in the charge balancing. These findings are supported by many-body cluster calculations.