We report anisotropic magnetodielectric coupling in layered van der Waals antiferromagnetic ${\mathrm{FePS}}_3$ (Néel temperature $T_N\sim$ 120 K) with perpendicular anisotropy. Above $T_N$, while the dielectric response function along the $c$ axis shows frequency-dependent relaxations, in-plane data is frequency independent and reveals a deviation from phonon-anharmonicity in the ordered state, thereby implying a connection to spin-phonon coupling known to be indicative of onset of magnetic ordering. At low temperature (below 40 K), atypical anomaly in the dielectric constant is corroborated with temperature-dependent dc and ac susceptibility. The magnetodielectric response across this anomaly differs significantly for both in-plane and out-of-plane cases. We have explained this in terms of preferential orientation of magnetic antiferromagnetic zigzag alignment, implied by the in-plane structural anisotropy as confirmed by ab initio calculations. Controlling the relative strength of magnetodielectric coupling with magnetic anisotropy opens a strategy for tracking subtle modifications of structures, such as in-plane anisotropy, with potential applications for spintronic technologies.

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• Dielectric properties
• First-principles calculations
• Magnetic anisotropy
• Spin-phonon coupling
• 2-dimensional systems
• Antiferromagnets
• Magnetic insulators