Spin-lattice-coupled order in Heisenberg antiferromagnets on the pyrochlore lattice

TL;DR

This study uses Monte Carlo simulations to show how local lattice distortions influence spin ordering in Heisenberg antiferromagnets on the pyrochlore lattice, revealing two distinct ordered states driven by spin-lattice coupling.

Contribution

It demonstrates that spin-lattice coupling induces first-order transitions into different collinear magnetic states with specific lattice distortions in pyrochlore antiferromagnets.

Findings

Stronger SLC leads to cubic symmetric magnetic order.

Weaker SLC results in tetragonal symmetric magnetic order.

Both states are accompanied by local lattice distortions.

Abstract

Effects of local lattice distortions on the spin ordering are investigated for the antiferromagnetic classical Heisenberg model on the pyrochlore lattice. It is found by Monte Carlo simulations that the spin-lattice coupling (SLC) originating from site phonons induces a first-order transition into two different types of collinear magnetic ordered states. The state realized at stronger SLC is cubic symmetric characterized by the magnetic (1/2,1/2,1/2) Bragg peaks, while that at weaker SLC is tetragonal symmetric characterized by the (1,1,0) ones, each accompanied by the commensurate local lattice distortions. Experimental implications to chromium spinels are discussed.