Effects of Ga and Cd Substitutions for Zn in PrIr2Zn20 on the Quadrupole-Driven Non-Fermi Liquid Behaviors
Abstract
The praseodymium-encaged compound PrIr2Zn20 with a non-Kramers doublet ground state undergoes an antiferroquadrupolar transition at TQ = 0.11 K. On heating above TQ, the magnetic specific heat Cm/T decreases as -ln T and the electrical resistivity ρ(T) increases with an upward curvature; thereby, formation of the quadrupole Kondo lattice is proposed. In this work, we studied the mechanism of these non-Fermi liquid (NFL) behaviors by measuring C and ρ for alloy systems where the Zn cage was partially substituted by Cd and Ga: PrIr2Zn20-xCdx (x ≤ 0.3) and PrIr2Zn20-yGay (y ≤ 0.25). The cubic lattice parameter increases with increasing x but hardly changes with y. The characteristic temperature T0 of the NFL behaviors in Cm(T), which is defined as the temperature where the magnetic entropy Sm(T) reaches (3/4)R ln 2, increases with increasing x and y. This increase in T0 is caused by the symmetry lowering of the Pr site due to the disorder of the cage atoms. On the other hand, another characteristic temperature, TR, where ρ(T) deviates from the T-linear dependence on cooling, decreases with increasing x but increases with y. This trend of TR indicates that the quadrupole Kondo lattice is stabilized owing to the strengthening of the c-f hybridization by the chemical pressure and/or the enhanced density of states of the conduction electrons.
- Publication:
-
Journal of the Physical Society of Japan
- Pub Date:
- May 2019
- DOI:
- 10.7566/JPSJ.88.054704
- Bibcode:
- 2019JPSJ...88e4704Y