Stripe order and magnetic anisotropy in the $S=1$ antiferromagnet BaMoP$_2$O$_8$

TL;DR

This study investigates the magnetic properties of BaMoP₂O₈, revealing stripe antiferromagnetic order driven by anisotropic spin interactions and one-dimensionality, with detailed experimental and computational analysis.

Contribution

It provides the first detailed characterization of magnetic order and anisotropy in BaMoP₂O₈ using combined experimental and theoretical methods.

Findings

Stripe antiferromagnetic order below 21 K

Strong in-plane coupling J₂ compared to J₁

Ordered magnetic moment reduced by quantum fluctuations and spin-orbit coupling

Abstract

Magnetic behavior of BaMoP$_2$O$_8$ with the spatially anisotropic triangular arrangement of the $S=1$ Mo$^{4+}$ ions is explored using thermodynamic measurements, neutron diffraction, and density-functional band-structure calculations. A broad maximum in the magnetic susceptibility around 46\,K is followed by the stripe antiferromagnetic order with the propagation vector ${\mathbf k}=(\frac{1}{2},\frac{1}{2},\frac{1}{2})$ formed below $T_N\simeq 21$ K. This stripe phase is triggered by a pronounced one-dimensionality of the spin lattice, where one of the in-plane couplings, $J_2\simeq 4.6$ meV, is much stronger than its $J_1\simeq 0.4$ meV counterpart, and stabilized by the weak easy-axis anisotropy. The ordered moment of 1.42(9) $\mu_B$ at 1.5 K is significantly lower than the spin-only moment of 2 $\mu_B$ due to a combined effect of quantum fluctuations and spin-orbit coupling.