Confirmation of a one-dimensional spin-1/2 Heisenberg system with ferromagnetic first-nearest-neighbor and antiferromagnetic second-nearest-neighbor interactions in Rb${}_{2}$Cu${}_{2}$Mo${}_{3}$O${}_{12}$

TL;DR

This study confirms Rb₂Cu₂Mo₃O₁₂ as a one-dimensional spin-1/2 Heisenberg system with competing ferromagnetic and antiferromagnetic interactions, showing a spin-singlet incommensurate ground state without magnetic phase transition down to 2 K.

Contribution

The paper provides experimental validation of Rb₂Cu₂Mo₃O₁₂ as a model for a 1D spin-1/2 Heisenberg system with specific competing interactions, highlighting its incommensurate ground state.

Findings

Estimated exchange interactions: J₁ = -138 K, J₂ = 51 K.

Ground state is a spin-singlet incommensurate state.

No magnetic phase transition observed down to 2 K.

Abstract

We have investigated magnetic properties of Rb$_2$Cu$_2$Mo$_3$O$_{12}$ powder. Temperature dependence of magnetic susceptibility and magnetic-field dependence of magnetization have shown that this cuprate is a model compound of a one-dimensional spin-1/2 Heisenberg system with ferromagnetic first-nearest-neighbor (1NN) and antiferromagnetic second-nearest-neighbor (2NN) competing interactions (competing system). Values of the 1NN and 2NN interactions are estimated as $J_1 = -138$ K and $J_2 = 51$ K ($\alpha \equiv J_2 / J_1 = -0.37$). This value of $\alpha$ suggests that the ground state is a spin-singlet incommensurate state. In spite of relatively large $J_1$ and $J_2$, no magnetic phase transition appears down to 2 K, while an antiferromagnetic transition occurs in other model compounds of the competing system with ferromagnetic 1NN interaction. For that reason, Rb$_2$Cu$_2$Mo$_3$O$_{12}$ is an ideal model compound to study properties of the incommensurate ground state that are unconfirmed experimentally.