Crystal Chemistry and Magnetic Properties of Manganese Zinc Alloy "YMn2Zn20" Comprising a Mn Pyrochlore Lattice

TL;DR

This study investigates the crystal structure and magnetic properties of YMn2Zn20, a manganese zinc alloy with a pyrochlore lattice, revealing complex magnetic interactions and the effects of elemental substitution and excess Mn atoms.

Contribution

It provides detailed insights into the composition, site preferences, and magnetic interactions in YMn2Zn20 and related compounds, highlighting the impact of excess Mn and substitutions on magnetic behavior.

Findings

Mn atoms in the pyrochlore lattice have small antiferromagnetic moments

No long-range magnetic order observed above 0.4 K due to geometrical frustration

Excess Mn atoms with large magnetic moments mask the inherent magnetism

Abstract

The chemical composition, crystal structure, and magnetic properties of a manganese zinc alloy with an ideal composition of YMn2Zn20, which comprises a pyrochlore lattice made of Mn atoms, are reported. The compound is stable only when In or Al is partially substituted for Zn. We have determined the actual chemical formula as YMn2+dZn20-x-dMx, with M = In or Al, and have identified the characteristic preferences with which the incorporated M and excess Mn atoms occupy the three crystallographic sites for Zn atoms. The Mn atoms in the pyrochlore lattice possess small magnetic moments that interact with each other antiferromagnetically but exhibit no long-range order above 0.4 K, probably owing to the geometrical frustration of the pyrochlore lattice. As a result, the effective mass of the conduction electrons is considerably enhanced, as observed in the related pyrochlore-lattice compounds (Y,Sc)Mn2 and LiV2O4. However, the presence of excess Mn atoms with large localized magnetic moments comparable to spin 5/2 tends to mask the inherent magnetism of the pyrochlore Mn atoms. It is suggested that "YMn2Zn18In2" with neither excess Mn atoms nor site disorder would be an ideal compound for further study.