A self-regulating magnetic fluid with a suitable second-order phase transition temperature for achieving hyperthermia treatment temperatures is investigated for use as a possible mild cancer treatment. Current studies have focused on the optimization of magnetic fluids. In this work, magnetic fluids of Al-doped Sr2FeMoO6 nanoparticles are investigated based on their relatively high saturation magnetization. The nanoparticles are synthesized using a simple sol–gel method, successfully nanomized, and then coated by oleic acid through ball milling to prevent oxidation and improve biocompatibility. The crystal structure, morphology, basic magnetic properties and heating properties of the samples in a high-frequency magnetic field are investigated. It is found that oleic acid-coated Sr1.98Al0.02FeMoO6 nanoparticles with a particle diameter of ~ 140 nm and a maximum heating temperature of 47.8 °C at a concentration of 2 mg·ml−1 possess excellent induction heating properties. The saturation magnetization, coercive force, specific absorption rate and effective specific absorption rate are 18 emu/g, 5.14 mT, 41.8 W·g−1 and 0.0193 W·g−1·kHz·(kA·m−2), respectively.