Effect of electron doping on the magnetic correlations in the bilayered brownmillerite compound Ca_{2.5-x}La_{x}Sr_{0.5}GaMn_{2}O_{8}: a neutron diffraction study

TL;DR

This neutron diffraction study reveals how electron doping via La substitution alters magnetic correlations in bilayered Ca2.5-xLaxSr0.5GaMn2O8, shifting from long-range to short-range antiferromagnetic order and lowering the Néel temperature.

Contribution

It provides new insights into the impact of electron doping on magnetic correlations and phase transitions in Brownmillerite-type compounds.

Findings

Electron doping induces short-range 3D AFM correlations above TN.

Doping decreases the Néel temperature (TN).

A magnetic phase diagram in x-T space is proposed.

Abstract

The effect of electron doping on the magnetic properties of the Brownmillerite-type bilayered compounds has been investigated by neutron powder diffraction in La substituted Ca2.5-xLaxSr0.5GaMn2O8 compounds (x = 0.05 and 0.1), in comparison with the undoped compound (x = 0). In all compounds, a long-range three dimensional collinear antiferromagnetic (AFM) structure is found below the N\'eel temperature TN of respective compound, whereas, well above TN, three dimensional short-range magnetic ordering is observed. In the intermediate temperature range just above TN, a strong effect of electron doping (La substitution) on the magnetic correlations has been observed. Here, a short-range AFM correlation with possible dimensionality of three has been found for substituted compounds (x = 0.05 and 0.1) as compared to the reported two dimensional long-range AFM ordering in the parent compound. With increasing the electron doping, a decrease in TN is also observed. The short-range magnetic correlations set in over a large temperature range above TN. A magnetic phase diagram in the x-T plane is proposed from these results.