Magnetic behavior of yavapaiite-type ${\mathrm{BaMoP}}_2{\mathrm{O}}_8$ with the spatially anisotropic triangular arrangement of the $S=1{\mathrm{Mo}}^{4+}$ 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.

• Received 25 June 2018
• Revised 13 August 2018

DOI:https://doi.org/10.1103/PhysRevB.98.094406