Large Easy Axis Anisotropy in the One-Dimensional Magnet BaMo(PO${}_4$)${}_2$

Abstract

We present an extensive experimental and theoretical study on the low-temperature magnetic properties of the monoclinic anhydrous alum compound BaMo(PO${}_4$)${}_2$. The magnetic susceptibility reveals strong antiferromagnetic interactions ${\theta }_{CW}=-167$~K and long-range magnetic order at $T_N=22$~K, in agreement with a recent report. Powder neutron diffraction furthermore shows that the order is collinear, with the moments near the $ac$ plane. Neutron spectroscopy reveals a large excitation gap $\Delta =15$~meV in the low-temperature ordered phase, suggesting a much larger easy-axis spin anisotropy than anticipated. However, the large anisotropy justifies the relatively high ordered moment, Néel temperature, and collinear order observed experimentally, and is furthermore reproduced in a first principles calculations using a new computational scheme. We therefore propose BaMo(PO${}_4$)${}_2$ to host $S=1$ antiferromagnetic chains with large easy-axis anisotropy, which has been theoretically predicted to realize novel excitation continua.

11 pages, 7 figures

References in corpus (3)

• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• Quantum Phase Diagram and Excitations for the One-Dimensional S=1 Heisenberg Antiferromagnet with Single-Ion Anisotropy
• One dimensionalization in the spin-1 Heisenberg model on the anisotropic triangular lattice

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