[en] In this work, Pr_xFe₉₄-_xB₆ (x = 6, 8, 10 and 12) nanostructured powders were prepared by a combination of hydrogenation, disproportionation, desorption and recombination (HDDR) process with high energy milling applied to the mixture of an as-cast alloy (Pr₁₄Fe₈₀B₆) and α-Fe. The produced nanoparticles showed magnetic properties comparable to those reported in hyperthermia studies. The optimal time to obtain the magnetic nanoparticles is 5 hours (at 900 rpm). It was verified that longer milling times cause an increase in carbon percentage on the particles. The carbon is derived from oleic acid added as a surfactant in the milling step. The nanocomposites exhibit coercive force ranging from 80 Oe (6.5 kAm^-1) to 170 Oe (13.5 kAm^-1) and magnetic moments in the range of 81 129 Am2kg^-1. From the X-ray diffraction analyses, only two phases were found in all samples: α-Fe and the magnetic phase Pr₂Fe₁₄B. Individual nanoparticles with diameter of about 20 nm were verified. The samples studied presented heating when exposed to an alternating magnetic field (f = 222 kHz e H_max ∼3.7 kAm^-1) comparable to reported in literature. Temperature variations (ΔT) of the powders were: 51 K for Pr₆Fe₈₈B₆, 41 K for Pr₈Fe₈₆B₆, 38 K for Pr₁₀Fe₈₄B₆ and T = 34 K for Pr₁₂Fe₈₂B₆. The specific absorption rates (SARs) of the powders were 201 Wkg^-1 for Pr₆Fe₈₈B₆ composition, 158 Wkg^-1 on the composition Pr₈Fe₈₆B₆, and 114 Wkg^-1 for Pr₁₀Fe₈₄B₆ and Pr₁₂Fe₈₂B₆ compositions. (author)