Noncoplanar spin canting in lightly-doped ferromagnetic Kondo lattice model on a triangular lattice

TL;DR

This study explores how mobile carriers influence magnetic order in a frustrated triangular lattice Kondo model, revealing that electron doping induces noncoplanar spin states with net magnetization, unlike hole doping.

Contribution

It demonstrates the emergence of noncoplanar spin canting due to electron doping in a frustrated Kondo lattice, highlighting the competition between magnetic interactions.

Findings

Electron doping destabilizes 120° antiferromagnetic order.

Induces noncoplanar umbrella-type spin configuration.

Hole doping preserves the 120° order up to finite doping.

Abstract

Effect of the coupling to mobile carriers on the 120$^\circ$ antiferromagnetic state is investigated in a ferromagnetic Kondo lattice model on a frustrated triangular lattice. Using a variational calculation for various spin orderings up to a four-site unit cell, we identify the ground-state phase diagram with focusing on the lightly-doped region. We find that an electron doping from the band bottom immediately destabilizes a 120$^\circ$ coplanar antiferromagnetic order and induces a noncoplanar three-sublattice ordering accompanied by an intervening phase separation. This noncoplanar phase has an umbrella-type spin configuration with a net magnetic moment and a finite spin scalar chirality. This spin-canting state emerges in competition between the antiferromagnetic superexchange interaction and the ferromagnetic double-exchange interaction under geometrical frustration. In contrast, a hole doping from the band top retains the 120$^\circ$-ordered state up to a finite doping concentration and does not lead to a noncolpanar ordering.