With the increasing demand of new magnetic materials for modern technological application alternatives to conventional magnetic materials, the development of lightweight polymer magnetic composites has become a prominent research area. For this perspective, a new magnetic material was developed using 30 wt% nickel ferrite micro and nanoparticles as fillers for a high-density polyethylene matrix. The development process began with the synthesis of NF-micro and NF-nanoparticles using solid-state and co-precipitation techniques, respectively, followed by extrusion molding and injection molding. The success of the synthesis process and the purity of the spinel structure phase were confirmed. Additionally, using the extrusion process produced polymer magnetic composite materials with a good distribution of magnetic particles within the polymer matrix, resulting in good magnetic properties and enhanced mechanical properties of the polymer magnetic materials.