The role of rare earth elements in tailorable thermal and magnetocaloric properties of RE-Co-Al (RE = Gd, Tb, and Dy) metallic glasses

•RE55Co17.5Al27.5 (RE = Gd, Tb, Dy) metallic glass rods with the critical diameters of 8 mm were fabricated.•With the replacement of gd by tb and dy elements, the thermal stability can be effectively improved.•Dy55Co17.5Al27.5 performs a high cooling efficiency in the hydrogen liquefaction temperature range.•The positive correlation between the Tg and the 4f electron number was demonstrated. RE55Co17.5Al27.5 (RE = Gd, Tb, and Dy) metallic glass (MG) rods with critical diameters of 8 mm were successfully fabricated by the copper-mold suction casting method. With the replacement of Gd by Tb and Dy, the thermal stability is improved, while the Curie temperature (Tc) decreases, which is attributed to the strong f-d hybridization and weak magnetic exchange interaction between Co and Tb/Dy. The reversed trend of the glass transition temperatures Tg and Tc was further discussed based on around 33 RE-based MGs for the competition between the dominant thermal effect and magnetic exchange interaction. Dy55Co17.5Al27.5 with a relatively strong dynamic behavior and wide supercooled liquid region of 66 K performs a high cooling efficiency in the hydrogen liquefaction temperature range ascribed to its low Tc below 50 K and rapid response to the applied magnetic field due to the large 4f electron number and low G-factor.