Tuning Magnetism Through Stoichiometric Potassium Intercalation into VOCl

Layered van der Waals (vdW) materials, characterized by their interlayer vdW gaps, offer exceptional tunability of magnetic properties via intercalation chemistry. A wide range of magnetic behaviors have been observed in nonmagnetic transition-metal dichalcogenides intercalated with magnetic atoms. Beyond the incorporation of magnetic ions, we propose the controlled alkali-ion intercalation of intrinsic vdW magnets as a strategy to probe and manipulate spin populations and exchange interactions within individual magnetic layers. Unlike conventional solid-state methods typically used for atomic intercalation, this approach depends on postsynthetic, solution-based reactions, which remain relatively underdeveloped and present unique synthetic challenges. Hence, in this work, we demonstrate precise potassium intercalation of VOCl, a layered antiferromagnet with square-like motifs, using stoichiometric organic reductants, potassium naphthalene and potassium pyrene. Our synthetic approach addresses thermodynamic and kinetic challenges via redox-matching reductants and electrolyte-assisted homogenization. Magnetic measurements reveal a continuous evolution from antiferromagnetism (x = 0) to a spin-glass state (0 < x < 1) with magnetic memory and ultimately to ferrimagnetism (x = 1) in K_xVOCl (0 ≤ x ≤ 1). Ab initio calculations support the existence of a spin-glass state, stabilized by mixed valence and competing magnetic interactions. Taken all together, this work establishes a programmable intercalation methodology to access metastable phases and tailor magnetic properties, offering new insights into magnetism in layered compounds with complex spin interactions.