The magnetization reversal in a ferromagnetic material occurs by (in)-coherent rotations or through magnetic domain wall movements. Both mechanisms rely on intrinsic and extrinsic, i.e. microstructure dependent, parameters. Experimentally we can measure the intrinsic properties (saturation magnetization (Ms), magnetocrystalline anisotropy and Curie point) in any polycrystalline material and the extrinsic properties of a magnet (coercivity (Hc), remanence, energy product (BH)max) in specific nanostructured samples. To get high-energy permanent magnets the materials must present high saturation (Ms
>100A·m2/kg) and anisotropy (Ha >5T), but also high extrinsic properties, like (BH)max >200kJ/m3. We are reviewing the effect of the modification of the microstructure on the coercivity of RE-lean magnets. In 2:14:1 phases, after infiltration, we can obtain values of coercivity (Hc =2.5T), which represent a large fraction of the anisotropy field (≈37%). However, for 1:12-phases, the coercivity is still low, around Hc =0.5T, for samples with Ha >10T.