# High-Temperature Layered Modification of Mn2In2Se5

## TL;DR

Scientists discovered a new high-temperature form of Mn2In2Se5 with unique magnetic properties, which could be useful for spintronics applications.

## Contribution

The synthesis and characterization of a new high-temperature polymorph of Mn2In2Se5 with antiferromagnetic properties.

## Key findings

- A new polymorph of Mn2In2Se5 with a primitive trigonal lattice was synthesized at 711 °C.
- The new structure crystallizes in the Mg2Al2Se5 type and shows antiferromagnetic behavior at 6.3 K.
- Magnetic frustration is indicated by a high |θ|/TN ratio of 28.

## Abstract

Layered chalcogenides are interesting from the point of view of the formation of two-dimensional magnetic systems for relevant applications in spintronics. High-spin Mn2+ or Fe3+ cations with five unpaired electrons are promising in the search for compounds with interesting magnetic properties. In this study, a new layered modification of the Mn2In2Se5 compound from the A2B2X5 family (“225”) was synthesized and investigated. A phase transition to the polymorph with primitive trigonal lattice was recorded at a temperature of 711 °C, which was confirmed by simultaneous thermal analysis, X-ray powder diffraction at elevated temperatures, and sample annealing and quenching. The stability of Mn2In2Se5 in air at high temperatures was investigated by thermal gravimetric analysis and powder X-ray diffraction. The new polymorph of Mn2In2Se5 crystallizes in the Mg2Al2Se5 structure type, as revealed by the Rietveld refinement against powder X-ray diffraction data. The crystal structure can be viewed as a close-packing of Se anions, in which indium and manganese cations are enclosed inside tetrahedral and octahedral voids, respectively, according to the AMnBInCBInCMnA… sequence. Magnetization measurements reveal an antiferromagnetic-like transition at a temperature of 6.3 K. The same magnetic properties are reported in the literature for the low-temperature R-centered trigonal polymorph. An approximation by the modified Curie–Weiss law yields a significant ratio of |θ|/TN = 28, which indicates strong magnetic frustration.