Highly Anisotropic Strain Dependencies In Prir2zn20

We report thermal expansion and magnetostriction of the cubic non-Kramers system PrIr2Zn20 with a nonmagnetic Gamma(3) ground-state doublet. In previous experiments, antiferroquadrupolar order at T-Q = 0.11 K and a Fermi liquid state at around B-c approximate to 5 T for B parallel to [001], indicative of possible ferrohastatic order, were discovered. For magnetic fields B parallel to [001], the low-temperature longitudinal and transverse thermal expansion and magnetostriction are highly anisotropic. The resulting volume strain is very small, indicating that the Pr valence remains nearly constant as a function of magnetic field. We conclude that the Fermi liquid state around B-c forms through a very little change in c- f hybridization. This result is in sharp contrast to Ce- and Yb-based Kramers Kondo lattices, which show significantly larger volume strains due to the high sensitivity of the Kondo temperature to hydrostatic pressure.