Insulators containing chains of magnetic transition metal cations provide platforms for probing spin-$\frac{1}{2}$ dynamics and quantum critical behavior. ${\mathrm{Li}}_2{\mathrm{CoCl}}_4$ contains edge-sharing ${\mathrm{CoCl}}_6$ octahedra that form chains along the crystallographic $c$ axis and orders antiferromagnetically at zero field, but questions remain about its applied-field magnetic structure and the ${\mathrm{Co}}^{2+}$ spin state. Here, we show with neutron diffraction on a polycrystalline sample how the antialigned chains of cobalt moments begin to transition to a ferromagnetic state above 1.6 T. Further, using magnetic resonance absorption measurements and noninteracting spin models, we reveal the strongly anisotropic nature of the ${\mathrm{Co}}^{2+}$ ion's $XY$-like magnetic behavior ($g_{\parallel }=2.77$ and $g_{\perp }=5.23$) and its $J=\frac{1}{2}$ ground state. We therefore supply the magnetic structures and anisotropic description needed to explore the dynamics of the field-driven magnetic phases, laying the foundation for further experimental and theoretical studies.

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• Magnetic anisotropy
• Magnetic order
• Magnetism
• Infrared spectroscopy
• Neutron diffraction