Exprimental And Theoretical Studies On The Related Physical Properties Of REAgSb₂ Intermetallics

The related physical properties of REAgSb₂?RE=La-Sm,Gd-Er?compounds are investigated on their polycrystalline samples by experimental measurements methods combining with theory calculation.The REAgSb₂ series samples were successfully prepared by using a vacuum arc melting furnace.The X-ray powder diffraction analysis shows that all sample contained REAgSb₂compounds,which crystallize in a tetragonal crystal structure with space group P4/nmm?No.129?.The results of magnetic measurements reveal that La Ag Sb₂is non-magnetic,Ce Ag Sb₂ exhibits ferromagnetic,and other compounds show antiferromagnetic.The magnetic ordering temperatures were obtained by d M/d T,which are distributed between 3.2 and 14.2 K.According to Curie-Weiss law,it was found that the effective magnetic moment of these alloys are close to rare earth trivalent ions in REAgSb₂.The metamagnetic transitions are observed for REAgSb₂?RE=Pr,Gd-Ho?according to M-H curves at 2K.The Arrott plots reveal that the magnetic phase transition type belong to second-order phase transition for REAgSb₂?RE=Ce,Pr?compounds.The maximum magnetic entropy changes of Ce Ag Sb₂ and Pr Ag Sb₂ are 5.1 and 7.9 J kg^-1K^-1,respectively.The structure,mechanical property,phonon,thermodynamic properties and electronic structure of REAgSb₂?RE=La-Sm,Gd-Er?compounds are studied using first principle calculation.According to the fitting results of Birch-Murnagha equation,it is found that REAgSb₂exhibits magnetic order except La Ag Sb₂ being non-magnetics.Besides,REAgSb₂ shows that the energy of anti-ferromagnetic state is lower than that of ferromagnetic state except Ce Ag Sb₂ and Gd Ag Sb₂.The calculated value of the cohesive energy of these alloys are all negative,indicating that they have stable structures.The calculated results of elastic modulus suggest that these compounds have stable mechanical properties.According to Poisson's ratio and B/G value,it can be verified that the Gd Ag Sb₂ and Tb Ag Sb₂ alloys perform toughness,while the remaining compounds are brittle.The phonon spectrum calculation results show that these compounds have stable thermodynamic properties.Their heat capacity C_Vsharply increases with temperature at low temperatures and is proportional to T³,and slowly increases at higher temperatures and tends to Dulong-Petit limit.The heat capacity at high temperature,which is close to 47.5 cal cell^-1K^-1.The calculated results of the electronic structures of REAgSb₂ suggest that the DOS dispersions are close to the RE 4f electrons and there is a strong correlation between RE and Sb atoms.The hybridization between RE 4f and Sb 5p electrons gradually increases as a function of atomic number for REAgSb₂?RE=Ce-Sm,Gd?,while gradually decreases for the other compounds.