Investigation Of Magnetic Properties And Magnetocaloric Effect In Ternary Rare-earth Based Amorphous Alloys

Refrigeration technology has an important position in modern society,and the exploration of new refrigeration technology has been receiving much attention.Magnetic refrigeration?MR?has the advantages of high efficiency,energy saving,environmental protection,stability and reliability.It is a new refrigeration technology with great potential,which has attracted the attention of many researchers.The basic principle is based on the magnetocaloric effect?MCE?of magnetic materials to exchange heat with the outside world.Research on MR materials with excellent performance is the focus of the development of MR technology.Rare earth-based amorphous alloys are attractive because of their good glass forming ability?GFA?and considerable MCE.This article selected the ternary rare earth-based amorphous alloys as the research objects,their structure,thermal stability,magnetic properties and MCE were reported in detail.The main research works and innovations are as follows:1.The RE₅₇Al₁₈Cu₂₅?RE= Ho,Tm?and RE₆₀Al₂₀Ni₂₀?RE= Ho,Er,Tm? amorphous ribbons were prepared by arc-melting and rapid quenching technique with the copper wheel,respectively.The structure and glass forming ability were studied by XRD,DSC and TEM.The results suggest that all the ribbons are completely amorphous state with good glass forming ability?GFA?.2.The initial crystallization temperature?T_x?values of RE₅₇Al₁₈Cu₂₅?RE=Ho,Tm?amorphous ribbons are 599 K and 631 K,respectively.And the T_x values of RE₆₀Al₂₀Ni₂₀?RE=Ho,Er,Tm?amorphous ribbons are 634.4 K,652.3 K and 663.2K.All the T_x are much larger than room temperature.So,those ribbons have higher structure stabilities at room temperature,having the potential to become a magnetic refrigeration material.3.The magnetic properties and MCE of RE₅₇Al₁₈Cu₂₅?RE= Ho,Tm? amorphous alloys were studied.The results show that the Curie temperature?T_C?values of Ho₅₇Al₁₈Cu₂₅ and Tm₅₇Al₁₈Cu₂₅ amorphous ribbons are 22.8 K and 5.4 K,respectively.A ferromagnetic-paramagnetic secondary phase transition occurs near the Curie temperatures,and no obvious thermal hysteresis is found.Under the same conditions,the peak value of the magnetic entropy change of Ho₅₇Al₁₈Cu₂₅ is slightly smaller than that of Tm₅₇Al₁₈Cu₂₅,but its magnetic entropy change curve changes more smoothly with temperature,making it have a higher refrigerant capacity?RC?.The maximum magnetic entropy change(-?35?S_M^{m ax})values under an external magnetic field change??35?H?of 0-5 T are 11.8 J/kg·K and 15.4 J/kg·K and the relative cooling power?RCP?are 482 J/kg and 301 J/kg for Ho₅₇Al₁₈Cu₂₅ and Tm₅₇Al₁₈Cu₂₅,respectively.The results show that RE₅₇Al₁₈Cu₂₅?RE=Ho,Tm?amorphous alloys have some advantages in low temperature MR materials.4.The magnetic properties and MCE of RE₆₀Al₂₀Ni₂₀?RE=Ho,Er,Tm?amorphous alloy were studied.The results show that the T_C values are 17.9 K,9.5 K and 4.4 K for Ho₆₀Al₂₀Ni₂₀ and Er₆₀Al₂₀Ni₂₀,and Tm₆₀Al₂₀Ni₂₀,respectively.A second-order magnetic phase transition?FM-PM?was found near their own T_Ctemperature.From Curie-Weiss law,we can see that ferromagnetic interaction dominates the alloy structure.According to the average field theory,Tm₆₀Al₂₀Ni₂₀amorphous ribbon is more uniform than Ho₆₀Al₂₀Ni₂₀ and Er₆₀Al₂₀Ni₂₀,and Ho₆₀Al₂₀Ni₂₀ has the highest field dependence,structural disorder is the largest,and the phase transition temperature span is wider.5.The RE₅₇Al₁₈Cu₂₅?RE= Ho,Tm?and RE₆₀Al₂₀Ni₂₀?RE= Ho,Er,Tm? amorphous alloys have good thermal stability and GFA,as well as excellent magnetic RC in the low temperature working area.These conclusions indicate that RE₅₇Al₁₈Cu₂₅?RE=Ho,Tm?and RE₆₀Al₂₀Ni₂₀?RE=Ho,Er,Tm?amorphous alloys have the potential to become low-temperature MR materials.