This is the first report ever on La3+-Nd3+ doped M-type hexaferrite nanoparticles: SrNdxLayFe12-x-yO19 (0 <= x <= 1) prepared by citrate precursor using the sal-gel technique followed by gel to crystallization. The substitution effects of ions and molar ratio of Fe3+/Sr2+ on the formation of ferrite phase were examined using powder differential thermal analysis (DTA) technique, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (Mid-IR) and vibrating sample magnetometer (VSM). The present work aim to study the crystallization of binary La3+-Nd3+ doped hexaferrite nanoparticles. DTA technique was employed to investigate the formation of nanocrystalline SrNd0.4La0.4Fe11.2O19 and revealed that the formation of ferrite phase was occurred in steps and crystallization take place by the means of endothermic reactions. The value of activation energy and crystallization temperature has been obtained from DTA data using different non-isothermal methods. XRD and Mid-IR studies have confirmed the formation of ferrite phase. Through this work an optimum calcination condition was established for the synthesis of single phase hexaferrite nanoparticles even after the substitution of binary rare earth elements. Magnetic properties were determined by using a vibrating sample magnetometer. The magnetic results revealed that the synthesized nanoparticles are suitable for perpendicular recording media due to their high coercivity value. (C) 2015 Elsevier B.V. All rights reserved.