Impurity Effects in Highly Frustrated Diamond Lattice Antiferromagnets

TL;DR

This paper investigates how dilute impurities influence the magnetic ground states of highly frustrated diamond lattice antiferromagnets, revealing mechanisms for impurity-induced order and stability criteria.

Contribution

It introduces a general argument and a numerical 'swiss cheese model' analysis showing impurities induce order and break degeneracy in frustrated antiferromagnets.

Findings

Dilute impurities induce magnetic order in frustrated systems.

A 'swiss cheese model' predicts impurity effects on ground state selection.

Criteria for stability against spin glass states are established.

Abstract

We consider the effects of local impurities in highly frustrated diamond lattice antiferromagnets, which exhibit large but non-extensive ground state degeneracies. Such models are appropriate to many A-site magnetic spinels. We argue very generally that sufficiently dilute impurities induce an ordered magnetic ground state, and provide a mechanism of degeneracy breaking. The states which are selected can be determined by a "swiss cheese model" analysis, which we demonstrate numerically for a particular impurity model in this case. Moreover, we present criteria for estimating the stability of the resulting ordered phase to a competing frozen (spin glass) one. The results may explain the contrasting finding of frozen and ordered ground states in CoAl2O4 and MnSc2S4, respectively.