We report the crystal structure and magnetic properties of a $S=\frac{3}{2}$ anisotropic triangular lattice compound ${\mathrm{Na}}_3\mathrm{Cr}$(${\mathrm{PO}}_4{)}_2$ employing single-crystal and powder x-ray diffraction, magnetization, heat capacity, and ${}^{31}\mathrm{P}$ nuclear magnetic resonance (NMR) experiments, supported by band structure calculations. Magnetic susceptibility exhibits a broad maximum at around 3.5 K, indicating the presence of a short-range antiferromagnetic order, typical of a low-dimensional spin system. Magnetization and heat capacity manifest an antiferromagnetic long-range ordering at around $T_{\mathrm{N}}\simeq 2.6\mathrm{K}$. This was further confirmed by the drastic NMR line broadening and a peak in the nuclear spin-lattice and spin-spin relaxation rates. The isothermal magnetization data exhibit a field-induced transition at around ${\mu }_0{H}_{\mathrm{SF}}\simeq 1.7\mathrm{T}$ reminiscent of an anisotropic two-dimensional magnet, before saturating above ${\mu }_0{H}_{\mathrm{sat}}\simeq 4.5\mathrm{T}$. The saturation field was further upheld by the field-dependent NMR relaxation measurements at low temperatures. The ${}^{31}\mathrm{P}$ NMR spectral shape confirms the commensurate antiferromagnetic nature of the ordering below $T_{\mathrm{N}}$. Ab initio calculations reveal a significant deformation of the triangular spin lattice, resulting in triangles with two antiferromagnetic couplings of similar strength and a much weaker coupling along the third side of the triangle.

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• Antiferromagnetism
• Frustrated magnetism
• Quantum phase transitions
• Nuclear magnetic resonance