Clustering induced suppression of ferromagnetism in diluted magnets

TL;DR

This paper demonstrates that impurity spin clustering in diluted magnets suppresses ferromagnetism by weakening bulk spin couplings, leading to magnon softening and reduced Curie temperature.

Contribution

It introduces a self-consistent magnon renormalization approach to analyze how impurity clustering affects magnetic order in diluted magnets.

Findings

Impurity spin clusters weaken bulk spin couplings.

Magnon softening occurs due to hole accumulation in clusters.

Curie temperature is reduced despite intra-cluster correlations.

Abstract

Ferromagnetism in diluted magnets in the compensated regime p << x is shown to be suppressed by the formation of impurity spin clusters. The majority bulk spin couplings are shown to be considerably weakened by the preferential accumulation of holes in spin clusters, resulting in low-energy magnon softening and enhanced low-temperature decay of magnetic order. A locally self-consistent magnon renormalization analysis of spin dynamics shows that although strong intra-cluster correlations tend to prolong global order, T_c is still reduced compared to the ordered case.