Cr_1/4NbSe₂-Single Crystal Growth and Evolution of Antiferromagnetic Correlated States

Transition-metal dichalcogenides provide a versatile platform for the intercalation of magnetic ions in their van der Waals gaps, enabling tuning of correlated electronic and magnetic states. Despite extensive studies on sulfide-based systems, Cr_xNbSe₂ remains poorly understood due to scarcity of single-crystals and uncertainties in structural analyses leading to contradictory reports on its magnetic behavior. Here, high-quality single crystals of Cr_1/4NbSe₂ via chemical vapor transport were synthesized, along with comprehensive investigation of chemical, structural, electronic, optical, electrical, and magnetic properties, supported by density-functional theory calculations, presented for the first time. Single crystal x-ray diffraction, scanning transmission electron microscopy, and selected area electron diffraction reveal ordered Cr intercalation forming a centrosymmetric 2 × 2 superlattice with hexagonal symmetry P6₃/mmc. Optical reflectivity indicates an enhanced electron scattering rate. DFT calculations predict antiferromagnetic ground state induced by Cr intercalation. Consistently, SQUID magnetometry and specific heat measurements hint a correlated antiferromagnetic state at T_N ≈ 107 K, while resistivity measurements show metallic transport, with no signatures of superconductivity. Electron spin resonance suggests weak internal field which possibly arise from subtle magnetic anisotropy, undetectable in angle-resolved magnetometry. These findings resolve longstanding inconsistencies and establish Cr_1/4NbSe₂ as a benchmark vdW antiferromagnet for next-generation spintronic and quantum materials.