Stoichiometry and Phase Control in K _{1– <i>x</i>} CrSe ₂ via Self-Flux Synthesis

Layered delafossite-type magnetic materials, such as KCrSe2, are promising platforms for studying magnetic systems and potential frustration on triangular lattices. Synthesis, structure-type control, and off-stoichiometries remain major challenges in the investigation of these delafossite-type magnets. Starting from the same self-flux composition (K:Cr:Se = 8:1:8), we isolated three distinct K1–xCrSe2 phases with x = 0, 0.13–0.17, and 0.32–0.35, each adopting a different structure type depending on the quenching temperature applied. The phase evolution indicates a sequence of transformations during synthesis between compounds with varying degrees of potassium deficiency. Building on these insights into phase stability and crystal growth, we successfully grew single crystals of full-stoichiometric KCrSe2─enabling direction-dependent magnetization measurements. These measurements reveal a pronounced field dependence of the Néel temperature at low external fields, as well as a weak metamagnetic transition. Our findings demonstrate that even a simple parameter─such as quenching temperature─can be used to control stoichiometry, direct phase formation, and ultimately tune the magnetic properties of delafossite-type materials.