Ordered States in Fcc Kagome Antiferromagnets with Magnetic Dipolar Interactions

TL;DR

This study explores various ordered magnetic states in fcc kagome antiferromagnets with both exchange and dipolar interactions, revealing novel vortex and glassy states influenced by the interaction strengths.

Contribution

It identifies new ordered states, including vortex and glassy states, arising from the interplay of exchange and dipolar interactions in fcc kagome antiferromagnets.

Findings

Vortex spin structure on hexagonal lattice points is discovered.

Glassy state with no apparent translational symmetry is identified.

Layered 120-degree spin structures depend on interaction ratios.

Abstract

Ordered states for a classical Heisenberg model on fcc lattice structure with ABC stacked kagome planes of magnetic ions are investigated by numerically solving the Landau-Lifshitz (LL) equation. Both the nearest-neighbor exchange interaction and the magnetic dipolar interactions are included in the model. The model with only the nearest-neighbor antiferromagnetic exchange interaction is known to show the layered 120 degree spin structure. On the other hand, the model with only the magnetic dipolar interactions is known to exhibit a continuous degeneracy expressed by six sublattice spin vectors, which is reduced by an order-by-disorder process with thermal fluctuations. In the present study, other ordered states appear for various values of relative strength of the two kinds of the interactions. A vortex spin structure on hexagonal lattice points in the kagomeplanes is a novel one. Another ordered state may be glassy state in which apparent translational symmetry cannot be seen. Layered 120 degree spin structures but not uniform in the direction perpendicular to the kagome planes with various period in the direction appear depending on the relative strength of the two kinds of the interactions.