© 2020 Chinese Society of Rare EarthsIn this comparative study, Tb and Tm substituted Sr-hexaferrites (HFs) with the chemical compositions of SrTbxFe12−xO19 and SrTmxFe12−xO19 (x = 0.00, 0.02 and 0.04) were fabricated via citrate sol-gel approach. The AC susceptibility and FC-ZFC magnetization were investigated. The product structure and morphologies were also investigated via XRD, TEM and SEM along with EDX. Measurements of temperature dependence of magnetization M-T and AC magnetic susceptibility versus temperature were carried out. The various synthesized HFs displayed ferrimagnetic behavior within 10–325 K. At lower temperatures, super-spin glass-like behavior was noticed. Neel-Arrhenius and Vogel-Fulcher models were employed to explore the experimental data of AC susceptibility.