Pressure Effects on Superconducting Quasiskutterudite Sr₃Rh₄Sn₁₃ Compared to the Ambient Pressure Properties of Ca₃Rh₄Sn₁₃ and La₃Rh₄Sn₁₃ Compounds

Herein, the transport properties of Sr₃Rh₄Sn₁₃, Ca₃Rh₄Sn₁₃, and La₃Rh₄Sn₁₃ quasi-skutterudites are studied which show sharp superconducting (SC) transition with a transition temperature, T_c, ≈4.7, ≈8, and ≈2 K, respectively. In Sr₃Rh₄Sn₁₃ system, electrical resistivity data evidence a pronounced anomaly before the SC transition at T* ≈136 K. No such anomalies are observed in the other two systems. Detailed structural investigations using synchrotron single-crystal and powder diffraction reveal that these systems have cubic structure with Sr₃Rh₄Sn₁₃ and Ca₃Rh₄Sn₁₃ being in PmPm (Formula presented.) n space group setting. The La₃Rh₄Sn₁₃ shows additional weak reflections which can be described by I4132 space group with almost doubled lattice parameters compared to Sr₃Rh₄Sn₁₃ system. All three systems are found to show weak Raman modes below 240 cm⁻¹. High-pressure (HP) resistivity measurements up to 3.2-GPa on Sr₃Rh₄Sn₁₃ system reveal that the T* anomaly decreases almost linearly with pressure whereas the superconducting T_c almost linearly increases. HP structural investigations on Sr₃Rh₄Sn₁₃ compound reveal that the structure remains in the cubic Pm (Formula presented.) n phase in 0–10 GPa range, following well a second-order Birch–Murnaghan equation of state. The results provide interesting similarities and differences in the chemical and physical pressure effects on the quasi-skutterudite X₃Rh₄Sn₁₃ (x = Sr, Ca, and La) system.