Highly anisotropic strain dependencies in PrIr2Zn20

We report thermal expansion and magnetostriction of the cubic non-Kramers system ${\mathrm{PrIr}}₂{\mathrm{Zn}}₂₀$ with a nonmagnetic ${\mathrm{\ensuremath{\Gamma}}}₃$ ground-state doublet. In previous experiments, antiferroquadrupolar order at ${T}_{\mathrm{Q}}=0.11$ K and a Fermi liquid state at around ${B}_{\mathrm{c}}\ensuremath{\approx}5\phantom{\rule{0.28em}{0ex}}\mathrm{T}$ for $\mathbit{B}\ensuremath{\parallel}[001]$, indicative of possible ferrohastatic order, were discovered. For magnetic fields $\mathbit{B}\ensuremath{\parallel}[001]$, 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 ${B}_{\mathrm{c}}$ forms through a very little change in $c\text{\ensuremath{-}}f$ 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.