Compressibility of $Ce M In_5$ and $Ce_2 M In_8$ (M = Rh, Ir and Co) Compounds

TL;DR

This study investigates how pressure affects the lattice parameters and superconducting properties of Ce$M$In$_{5}$ and Ce$_{2}M$In$_{8}$ compounds, revealing a universal relationship between $T_c$ and structural parameters.

Contribution

The paper provides new insights into the pressure-dependent lattice stiffness and hybridization in Ce-based compounds, establishing a universal $T_c$ versus $c/a$ relationship across different materials.

Findings

Lattice stiffness increases with added In$_2$ layers.

Dominant hybridization is $fp$ between Ce and In atoms.

Universal $T_c$ versus $c/a$ behavior observed across compounds.

Abstract

The lattice parameters of the tetragonal compounds Ce$M$In$_{5}$ and Ce$_{2}M$In$_{8}$($M=$Rh, Ir and Co) have been studied as a function of pressure up to 15 GPa using a diamond anvil cell under both hydrostatic and quasihydrostatic conditions at room temperature. The addition of $M$In$_{2}$ layers to the parent CeIn$_{3}$ compound is found to stiffen the lattice as the 2-layer systems (average of bulk modulus values $B_{0}$ is 70.4 GPa) have a larger $B_{0}$ than CeIn$_{3}$ (67 GPa), while the 1-layer systems with the are even stiffer (average of $B_{0}$ is 81.4 GPa). Estimating the hybridization using parameters from tight binding calculations shows that the dominant hybridization is $fp$ in nature between the Ce and In atoms. The values of $V_{pf}$ at the pressure where the superconducting transition temperature $T_{c}$ reaches a maximum is the same for all Ce$M$In$_{5}$ compounds. By plotting the maximum values of the superconducting transition temperature $T_{c}$ versus $c/a$ for the studied compounds and Pu-based superconductors, we find a universal $T_{c}$ versus $c/a$ behavior when these quantities are normalized appropriately. These results are consistent with magnetically mediated superconductivity.