Incommensurate and multiple-$\boldsymbol{q}$ magnetic misfit order in the frustrated quantum-spin-ladder material antlerite, Cu$_3$SO$_4$(OH)$_4$

TL;DR

This paper reveals complex magnetic phases, including incommensurate and multiple-q states, in the frustrated quantum-spin-ladder mineral antlerite, highlighting its high tunability and potential for exotic magnetic phenomena.

Contribution

It reports the discovery of multiple magnetic orders, including incommensurate and multiple-q phases, in antlerite, a highly frustrated quantum-spin-ladder material, expanding understanding of magnetic degeneracy effects.

Findings

Identification of incommensurate helical+cycloidal state in antlerite

Observation of a multiple-q magnetic phase analogous to misfit structures

Reentrant antiferromagnetic order on the central leg

Abstract

In frustrated magnetic systems, the competition amongst interactions can introduce extremely high degeneracy and prevent the system from readily selecting a unique ground state. In such cases, the magnetic order is often exquisitely sensitive to the balance among the interactions, allowing tuning among novel magnetically ordered phases. In antlerite, Cu$_3$SO$_4$(OH)$_4$, Cu$^{2+}$ ($S=1/2$) quantum spins populate three-leg zigzag ladders in a highly frustrated quasi-one-dimensional structural motif. We demonstrate that at zero applied field, in addition to its recently reported low-temperature phase of coupled ferromagnetic and antiferromagnetic spin chains, this mineral hosts an incommensurate helical+cycloidal state, an idle-spin state, and a multiple-$q$ phase which is the magnetic analog of misfit crystal structures. The antiferromagnetic order on the central leg is reentrant. The high tunability of the magnetism in antlerite makes it a particularly promising platform for pursuing exotic magnetic order.