Structural and magnetic properties of MSr2Y1.5Ce0.5Cu2Oz (M-1222) compounds with M = Fe and Co

TL;DR

This study investigates the structural and magnetic properties of MSr2Y1.5Ce0.5Cu2Oz compounds with M = Fe and Co, revealing site occupancy, oxidation states, and magnetic behavior through neutron diffraction and spectroscopy.

Contribution

It provides detailed site occupancy, oxidation states, and magnetic properties of Fe-1222 and Co-1222 compounds using neutron diffraction and Mossbauer spectroscopy.

Findings

Fe occupies two lattice sites with different oxidation states.

Co predominantly remains at its designated site with some site mixing.

Both compounds exhibit complex magnetic behavior as shown by magnetization curves.

Abstract

MSr2Y1.5Ce0.5Cu2Oz (M-1222) compounds, with M = Fe and Co, have been synthesized through a solid-state reaction route. Both compounds crystallize in a tetragonal structure (space group I4/mmm). A Rietveld structural refinement of room-temperature neutron diffraction data for Fe-1222 reveals that nearly half the Fe remains at the M site, while the other half goes to the Cu site in the CuO2 planes. Existence of Fe at two different lattice sites, is also confirmed by 57Fe Mossbauer spectroscopy from which it is inferred that nearly 50% of the total Fe occupies the Cu site in the CuO2 planes as Fe3+, whereas the other 50 % is located at the M site with nearly 40 % as Fe4+ and around 10% as Fe3+. For the M = Co compound, nearly 84 % of Co remains at its designated M site, while the rest occupies the Cu site in the CuO2 planes. The oxygen content, z, based on oxygen occupancies refined from the neutron diffraction data, comes close to 9.0 for both the samples The ZFC and FC magnetization curves as a function of temperature show a complex behavior for both Fe-1222 and Co-1222 compounds.