Cation intermixing and ordering phenomenon in MO layer of MSr2YCu2Oz (M1212) compounds with M = Fe, Co, Al, and Ga: A neutron powder diffraction study

TL;DR

This study investigates the structural and magnetic properties of MSr2YCu2Oz compounds with M = Fe, Co, Al, and Ga, revealing cation intermixing, ordering phenomena, and magnetic behaviors through neutron diffraction and magnetization analysis.

Contribution

It provides detailed structural insights into M1212 compounds, highlighting differences in cation distribution and magnetic ordering for various M elements.

Findings

Fe shows cation intermixing and magnetic ordering below 70 K.

Co compounds exhibit low-dimensional magnetic behavior below 150 K.

Al and Ga compounds are paramagnetic down to 5 K.

Abstract

Various MSr2YCu2Oz (M1212 with M = Fe, Co, Al and Ga) compounds have been synthesized through a solid state reaction route. All these compounds are derived from the basic CuBa2YCu2O7 structure. Rietveld structural refinement of the room-temperature neutron diffraction data for Fe-1212 reveals that nearly half of Fe remains at the M site, while the other half goes to the Cu site in the CuO2 plane. For the M = Co, Al and Ga compounds, the basic unit cell gets doubled due to two distinct M sites in the M-O layer and the space group Ima2, without any cation intermixing is found more appropriate. For the M = Fe sample, magnetic ordering of Fe spins is seen from magnetization data below 70 K. In the case of the M = Co compound, a shallow down-turn in magnetic susceptibility is seen below 150 K, indicating low dimensional magnetic characteristics of the CoO layer. The compounds with M = Al and Ga show paramagnetic behaviour in their magnetization data down to 5 K. The oxygen content, established for each compound based on oxygen occupancies, refined from the neutron diffraction data comes close to 7.0 for each.