The Gd0.05Fe2.95O4 nanoparticles were synthesized by seed - mediated growth and were reacted for 30, 45, 60 and 75 min (Gd30, Gd45, Gd60 and Gd75), respectively. The samples structural and magnetic properties were investigated by x-ray diffraction (XRD), vibrating sample magnetometry (VSM), and Mössbauer spectroscopy. The self-heating properties were investigated by using a MagneTherm device. According to XRD analysis, gadolinium (Gd) nanoparticles found to be a cubic spinel structure has a space group Fd-3m. The lattice constant (a0) of Gd nanoparticles are 8.3633 ˚A and increases to 8.3721 ˚A as the high-temperature reaction time increases. The particle size was determined using Scherrer’s equation and the maximum particle size was 10.84 nm. The maximum saturation magnetization (MS) value of Gd60 at room temperature was 63.10 emu/g. The self - heating temperature of Gd60 at 112 kHz and 250 Oe was measured and 63.3 °C was the highest. Gd60 had the largest particle size and highest MS and self-heating properties were measured. Mössbauer measurements were performed to investigate hyperfine interactions at from 4.2 to 290 K.