Correspondence on “Suppressing Energy Migration via Antiparallel Spin Alignment in One‐Dimensional Mn ²⁺ Halide Magnets with High Luminescence Efficiency”

Abstract The photoluminescence quantum yield (PLQY) of tetramethyl ammonium manganese(II) chloride, (CH 3 ) 4 NMnCl 3 (TMMC), doped with Cd 2+ /Cu 2+ is analyzed through photoluminescence measurements, X‐ray diffraction, optical absorption, and time‐resolved excitation and emission under hydrostatic pressure. Contrary to recent studies reporting a PLQY increase up to x = Cd x /Mn 1‐x = 0.08 followed by a decline (from 95% to 77% at x = 0.22), 1 we demonstrate that the PLQY remains consistently high (≥95%) across the concentration range x = 0–0.22.