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arXiv · 2209.15510

Single-crystal study of the honeycomb XXZ magnet BaCo$_2$(PO$_4$)$_2$ in magnetic fields

Xiao Wang·Rohit Sharma·Petra Becker·Ladislav Bohatý·Thomas Lorenz
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Abstract

We present a study of high-quality BaCo$_2$(PO$_4$)$_2$ single crystals via magnetization, heat-capacity, thermal-expansion and magnetostriction measurements. Sharp anomalies in the thermodynamic properties at $T_N=3.4\,$K reveal a long-range antiferromagnetic order in these single-crystalline samples, which is absent in polycrystalline BaCo$_2$(PO$_4$)$_2$. The temperature dependent magnetic susceptibilities for in-plane and out-of-plane magnetic fields are strongly anisotropic and reveal a pronounced easy-plane anisotropy. A Curie-Weiss analysis implies strong orbital magnetism, as it is known from the sister compound BaCo$_2$(AsO$_4$)$_2$ that is discussed as a potential Kitaev spin-liquid material. When applying in-plane magnetic fields at low temperature, BaCo$_2$(PO$_4$)$_2$ is driven to another ordered phase at a critical field $H_{C1}\approx 0.11\,$T and then undergoes a further field-induced transition to a highly polarized paramagnetic phase at $H_{C2}\approx 0.3\,$T, which is again similar to the case of BaCo$_2$(AsO$_4$)$_2$. In addition, our lowest-temperature data reveal that the field-induced transitions in BaCo$_2$(PO$_4$)$_2$ become dominated by thermally assisted domain-wall motion.

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Xiao Wang, Rohit Sharma, Petra Becker, Ladislav Bohatý, Thomas Lorenz. 2023-02-07. Single-crystal study of the honeycomb XXZ magnet BaCo$_2$(PO$_4$)$_2$ in magnetic fields. https://doi.org/10.1103/physrevmaterials.7.024402

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