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International audience; The influence of quenching rate and nitrogenation in melt-spun Nd 1.2 Fe 10.6 Mo 1.4 has been investigated in terms of microstructure, phase formation and magnetic properties. Increasing the quenching rate leads to smaller grain size. However, it also implies a change in the crystallized phase structure. We obtained a pure ThMn 12 (1:12) structure at quenching rates up to 30 m/s, leading to an average grain size of 220 nm. Magnetic measurements of the as-spun ribbons revealed a reduction of the saturation magnetization for samples quenched above 30 m/s. This is attributed to the formation of a paramagnetic phase and/or magnetic phase with a Curie temperature (Tc) close to room temperature which is confirmed by 57 Fe Mössbauer spectroscopy. The analysis of the spectra rules out the presence of a ferromagnetic TbCu7 (1:7) phase, which is usually reported in such system. The ribbons were nitrogenated in order to form the harder magnetic phase Nd 1.2 Fe 10.6 Mo 1.4 N x. The ribbon quenched at 30 m/s with the pure ThMn 12 nitride structure is the optimum sample for getting hard magnetic properties, with a coercivity of 0.6 T, saturation magnetization of 1.15 T and Curie temperature of 350 °C. Finally, we show the good stability of the later phase structure at elevated temperatures (≤ T C), making this compound a good candidate for permanent magnet applications.