Magnetic Properties And Magnetocaloric Effect Of Heavy Rare Earth Based Amorphous Materials

With the development of modern society,the traditional vapor-compression refrigeration technique has not met the growing needs of people,thus new refrigeration technologies have been focused.Magnetic refrigeration technology based on the magnetocaloric effect(MCE)has been considered as a potential promising cooling technology for its advantages like environmental friendliness,high conversion rate and reliable.Searching for novel magnetic solids with excellent magnetocaloric performance still the main target at present.Recentlly,the heavy rare earth(HRE)based amorphous materials have attracted much attention because of their unique physical structure,good glass forming ability,considerable MCE,etc.In this article,the crystal structure,glassy formation ability,magnetic properties and MCE in two series of HRE based amorphous materials have been systematically investigated.The results achievements are as follows:1.The RE₆₀Co₂₀Ni₂₀(RE=Ho,Er,Tm)and RE₆₀Co₂₀Al₂₀(RE=Ho,Er,Tm)amorphous ribbons were prepared by arc-melting and single copper melt-spinning technology.The amorphous nature has been confirmed by the X-ray diffraction and differential scanning calorimeter.2.The glass transition temperatures(T_g)values of Ho₆₀Co₂₀Ni₂₀,Er₆₀Co₂₀Ni₂₀and Tm₆₀Co₂₀Ni₂₀ are 621.5 K,567.3 K and 622.0 K,respectively.And the T_x values of the amorphous ribbons are 638.5 K,653.6 K and 650.0 K.Combined with the T_rg,?T_xand?parameters,it can be seen that all the ribbons are thermally stable,and they also have good glass forming ability.3.The curie temperatures(T_C)of Ho₆₀Co₂₀Ni₂₀,Er₆₀Co₂₀Ni₂₀ and Tm₆₀Co₂₀Ni₂₀are 20.4 K,11.5 K,and 6.7 K,respectively.Moreover,all ribbons undergo a second-order magnetic transition from ferromagnetic to paramagnetic(FM-PM)near this temperature,and there is no thermal hysteresis during the process.Under the external magnetic field change of 0-5 T,the-?S_M^{m ax}values are calculated to be 18.4,15.5,and17.1 J/kg·K for RE₆₀Co₂₀Ni₂₀(RE=Ho,Er,Tm)and the corresponding values of RCP are 668.2,403.2 and 273.0 J/kg,respectively.4.The initial crystallization temperature(T_x)values of RE₆₀Co₂₀Al₂₀(RE=Ho,Er,Tm)amorphous ribbons are much greater than room temperature,so all ribbons are stable at room temperature.In addition,the results show that the T_rgvalues are all close to 0.6,and the?T_x and?parameter values are also considerable.In summary,all ribbons have a great stability and good glass forming ability.5.The curie temperatures(T_C)of Ho₆₀Co₂₀Al₂₀,Er₆₀Co₂₀Al₂₀ and Tm₆₀Co₂₀Al₂₀are 22.3,10.3,and 5.0 K,respectively.All the ribbons are undergoing a second order FM to PM transition.For the?H of 0-7 T,the values of-?S_M^max are 14.2,15.6 and 15.1J/kg·K,and the corresponding values of RCP are 625.0,505.7and 334.0 J/kg,respectively.6.RE₆₀Co₂₀Ni₂₀(RE=Ho,Er,Tm)and RE₆₀Co₂₀Al₂₀(RE=Ho,Er,Tm)amorphous ribbons have great thermal stability and good glass forming ability.In addition,its comprehensive performances in terms of operating temperature range,maximum magnetic entropy change,and refrigerant capacity are also great.In a conclusion,both serious of ribbons are also considerable for magnetic refrigeration.