Investigation Of The Magnetic Properties And Magnetocaloric Effect In The Material Of Rare Earth Transition Group Perovskite Oxides

Compared with traditional refrigeration methods,magnetic refrigeration has the advantages of simple structure,environmental friendliness,and high work efficiency,and may become the development direction of future refrigeration technology.Some precision instruments,medical health,petrochemical and other fields cannot be separated from the low and medium temperature(≤77 K)environment.Especially high-tech scientific and technological research needs to be carried out at ultra-low temperature.Low-temperature magnetic refrigeration has broad prospects.Perovskite structure oxide system can show many strange and interesting physical phenomena through doping substitution and other means.This article mainly studies the magnetic and magnetocaloric effects of REFe0.5Cr0.5O3(RE=Gd,Tb,Dy)and RECo0.5Cr0.5O3(RE=Gd,Tb,Dy)perovskite-type oxides,and double perovskite Magnetism and magnetocaloric effect of type oxide SrzRENbO6(RE=Gd,Tb,Dy).REFe0.5Cr0.5O3(RE=Gd,Tb,Dy)perovskite oxide has a cubic structure and the space group is Pbnm.It was found that GdFe0.5Cr0.5O3 has a paramagnetic structure,TbFe0.5Cr0.5O3,DyFe0.5Cr0.5O3 perovskite-type oxides have an antiferromagnetic structure,and the Nair temperature(TN)is 8.5 K and 15.2 K.It is calculated that REFe0.5Cr0.503(RE=Gd,Tb,Dy)perovskite-type oxides under the applied magnetic field strength 0～5 T-△SMmax are 31.46 J/kg·K,10.99 J/kg·K,12.644 J/kg·K respectively.Compared to GdCrO3 and DyCrO3,the-△SMmax after doping has increased to some extent.The results prove that REFe0.5Cr0.5O3(RE=Gd,Tb,Dy)perovskite-type oxides have large low-temperature magnetocaloric effects,and there is no hysteresis.In particular,the low-temperature magnetic entropy of GdFe0.5Cr0.5O3 is relatively large,and has great application potential.RECo0.5Cr0.5O3(RE=Gd,Tb,Dy)perovskite oxide has a cubic structure and the space group is Pbnm.The study found that RECo0.5Cr0.5O3(RE=Gd,Tb,Dy)all have a paramagnetic structure.It is calculated that RECo0.5Cr0.5O3(RE=Gd,Tb,Dy)perovskite oxide under the applied magnetic field strength 0～5 T-△SMmax is 22.02 J/kg·K,6.19 J/kg·K,4.11 J/kg·K respectively.The results show that RECo0.5Cr0.5O3(RE=Gd,Tb,Dy)perovskite-type oxides have large low-temperature magnetocaloric effects,and there is no hysteresis.In particular,the low-temperature magnetic entropy of GdCo0.5Cr0.5O3 is relatively large,and has great application potential.Compared to REFe0.5Cr0.5O3(RE=Gd,Tb,Dy)perovskite-type oxides,RECo0.5Cr0.5O3(RE=Gd,Tb,Dy)perovskite-type oxides show significant magnetic entropy.The decrease indicates that the magnetocaloric effect of iron semi-doped RECrO3 is better than that of cobalt semi-doped RECrO3.However,the half-height width(δTFWHM)of the semi-doped RECrO3 is significantly improved,which indicates that the working temperature region of the material is larger and has important practical significance.Therefore,we guess that the codoping of Fe and Co can improve the magnetic entropy change of the material and the halfwidth at the same time,so that it can improve the low-temperature cooling capacity of the material.The Sr2RENbO6(RE=Gd,Tb,Dy)double perovskite oxide has a monoclinic crystal system,and the space group is P21/n.It was found that Sr2RENbO6(RE=Gd,Tb,Dy)has a paramagnetic structure.The calculated Sr2RENbO6(RE=Gd,Tb,Dy)double perovskite-type oxides under the applied magnetic field strength 0～5 T-△SMmax are 24.22 J/kg·K,2.02 J/kg·K and 10.64 J/kg·K respectively.The results vertify that Sr2GdNbO6 double perovskite oxide has large low-temperature magnetocaloric effect,and there is no hysteresis,which has great application potential.