Magnetic ordering and crystal field effects in theR2Ir3Sn5(R=La–Nd, Gd–Tm) system

Abstract

We report on the detailed magnetic properties of polycrystalline ternary rare-earth intermetallic stannide compounds $R$${}_{2}$Ir${}_{3}$Sn${}_{5}$ ($R$ $=$ La--Nd, Gd--Tm). Except for La${}_{2}$Ir${}_{3}$Sn${}_{5}$, all the other compounds of $R$${}_{2}$Ir${}_{3}$Sn${}_{5}$ ($R$ $=$ Ce--Nd, Gd--Tm) crystallize in the orthorhombic Y${}_{2}$Rh${}_{3}$Sn${}_{5}$(Cmc2${}_{1}$) type structure. La${}_{2}$Ir${}_{3}$Sn${}_{5}$ crystallizes in the U${}_{2}$Co${}_{3}$Si${}_{5}$ type orthorhombic crystal structure with the space group Ibam. Transport and magnetization measurements were done from 1.8 to 300 K and the heat-capacity measurement was done from 2 to 30 K. We found from the magnetic measurements that Ce${}_{2}$Ir${}_{3}$Sn${}_{5}$ is a Kondo system, which undergoes an antiferromagnetic ordering at 2.9 K, while no magnetic ordering was observed in Pr${}_{2}$Ir${}_{3}$Sn${}_{5}$ and Nd${}_{2}$Ir${}_{3}$Sn${}_{5}$ down to 1.8 K. The higher rare earths from Gd--Tm of this series exhibit magnetic ordering below 10 K. Crystal field analysis was done on both the magnetic susceptibility and heat capacity to find the crystal field level schemes. From the detailed magnetic measurements, we found that the magnetic ordering temperature deviates from the expected de Gennes scaling, which indicates that the RKKY interaction needs to be modified, including the crystal field effects, to account for this deviation.