Effect Of Different Elements Doping On Magnetocaloric Properties Of Gd-based Amorphous Alloys

Compared with traditional gas compression refrigeration,magnetic refrigeration has attracted widespread attention because of its characteristics of energy saving,high efficiency,environmental friendliness,reliable operation,etc.The choice of magnetic refrigerating medium is related to the temperature range and refrigerating capacity of magnetic refrigerating.Therefore,looking for the right working medium becomes the primary issue to be solved to promote the development of magnetic refrigeration.Amorphous alloys have been widely studied as magnetic working mediums for their adjustable magnetic phase transition temperature,small thermal hysteresis loss,high resistivity,etc.The rare earth based amorphous alloys are particularly prominent because of their big magnetocaloric effect.Based on this background,the thermal stability and magnetocaloric effects of Gd-based amorphous ribbons doped with different elements are studied systematically.Firstly,a series of Gd_70-xDy_xM₂₀Si₁₀(x=5,20;M=Fe,Co,Ni)amorphous ribbons with second-order magnetic phase transition were successfully prepared,and the thermal stability and magnetocaloric effect of the amorphous ribbons were studied by the doping of rare earth element Dy.We found that the Gd₆₅Dy₅M₂₀Si₁₀(M=Fe,Co,Ni)alloys with less Dy element show higher magnetic phase transition temperature,greater magnetic cooling capacity and better glass forming ability.Secondly,we prepared Gd₆₅Dy₅M₂₀Al₁₀(M=Fe,Co,Ni)amorphous ribbons with Al element instead of Si element to study the effect of different light elements on the magnetocaloric effect of Gd-based amorphous alloy.It was found that both Curie temperature and magnetic entropy change decrease when the Si was replaced by Al.However the Gd₆₅Dy₅M₂₀Al₁₀ amorphous alloys show wider temperature span than that of Gd₆₅Dy₅M₂₀Si₁₀amorphous ribbons,which enabled them to have larger refrigeration capacity,and the value of the refrigeration capacity(RC)of Gd₆₅Dy₅Fe₂₀Al₁₀ is 1039.2 J/kg.Finally,the influence of Fe doping on the thermal stability and magnetocaloric properties of Gd-based amorphous alloys were studied.The studies showed that the Curie temperature of the samples increased with the increase of Fe content,and the Curie temperature of Gd₄₅Dy₅Co₄₀Si₃Fe₇ reached to 286 K,approaching to the room temperature.Although the magnetic entropy of the amorphous alloys decreased with the increase of Fe content,however,they have a larger magnetic phase transition temperature range,which makes them have larg e refrigeration capacity.A table-like magnetic entropy change curve was observed in Gd₄₅Dy₅Co₄₀Si₃Fe₇ at the low temperature range,causing it has a high RC value of 823.2 J/kg,which promises it very competitive in magnetic refrigeration.