Supplementary Online Material

More detailed descriptions on (1) magnetic configurations and Curie temperatures; (2) the lattice constants, magnetic moment, and energy difference of different magnetic configurations of the optimized and stable TM-HOTP structures, the effect for Mn-HOTP under different Ueff and k-points mesh, the MAE, coupling constants and estimated Tc of doped and undoped Mn-HOTP, decomposition products for Mn-HOTP; (3) the band structures of other structures that were omitted in the main text file, the band structure calculated by TB and DFT with SOC, and the edge state of Mn-HOTP with SOC.