A new hybrid molecular-based ferromagnet of formula [(dmaph)PPh 3 ][MnCr(ox) 3 ], where [(dmaph)PPh 3 ] + stands for the (4-dimethylaminophenyl)triphenylphosphonium cation (ox 2being the oxalate anion), has been synthesized. It crystallizes in the monoclinic P2 1 space group, with lattice parameters a ) 13.954(2) Å, b ) 16.297(2) Å, c ) 14.323(2) Å, and β ) 99.27(1)°. Refinement based on F o 2 yields R ) 0.072 and wR 2 ) 0.156. The compound exhibits a ferromagnetic interaction between Cr 3+ and Mn 2+ , with a long-range magnetic ordering at T C ) 4.5 K. The hyperpolarizability (β) of the cation is calculated within the framework of the INDO/SOS-based method, which indicates a β value comparable to that of pnitroaniline for an absorption maximum at 306 nm ( max ) 28 500 M -1 cm -1 ). This result is consistent with the observation of a SHG efficiency 4 times that of urea for the parent [(dmaph)PPh 3 ]Br salt, at 1.907 µm. The non-centrosymmetric [(dmaph)PPh 3 ][Mn II Cr III (ox) 3 ] derivative is used as a model compound for an investigation of the potential effect of a ferromagnetic ordering on the bulk NLO response of hybrid materials made of NLO cations inserted between magnetic anionic layers.