Suppression of Superconductivity in PrRh2Zn20by the Substitution of Co for Rh

Electrical resistivity ρ, magnetic susceptibility χ and specific heat C of Pr(Rh1-xCox)2Zn20 for 0 ≤ x ≤ 0.89 were measured to study the mechanism of simultaneous superconducting and antiferroquadrupolar (AFQ) transitions at Tc = TQ = 0.06 K in PrRh2Zn20. A broad peak in the magnetic specific heat Cm(T) at around 13 K is reproduced as a Schottky peak by a doublet-triplet two-levels model. However, another broad peak in Cm(T) at 1 3 K indicates splitting of the doublet state by a slight distortion of Zn cages due to the Co substitution. As a consequence of the splitting, the quadrupolar degrees of freedom must be quenched. With increasing x, Tc = 0.06 K for x = 0 is suppressed below 0.04 K for x ≥ 0.10. The suppression of Tc suggests possible interplay between the superconductivity and the quadrupolar degrees of freedom.

[1]  T. Takabatake,et al.  Well-Defined Crystal Field Splitting Schemes and Non-Kramers Doublet Ground States offElectrons in PrT2Zn20(T= Ir, Rh, and Ru) , 2013 .

[2]  T. Hasegawa,et al.  First-principles calculations of lattice vibrations on LaT2Zn20 (T = Ru and Ir) , 2012 .

[3]  T. Takabatake,et al.  Nonmagnetic Γ3 doublet ground state in a caged compound PrRh2Zn20 , 2012 .

[4]  T. Sakakibara,et al.  Simultaneous superconducting and antiferroquadrupolar transitions in PrRh 2 Zn 20 , 2012, 1211.3183.

[5]  T. Takabatake,et al.  NMR Evidence of Freezing of Rattling Motion in LaIr2Zn20 and LaRu2Zn20 , 2012 .

[6]  M. Akatsu,et al.  Antiferro-Quadrupolar Ordering at the Lowest Temperature and Anisotropic Magnetic Field–Temperature Phase Diagram in the Cage Compound PrIr2Zn20 , 2011 .

[7]  T. Sakakibara,et al.  Antiferroquadrupolar ordering in a Pr-based superconductor PrIr(2)Zn(20). , 2011, Physical review letters.

[8]  Y. Matsushita,et al.  Superconductivity and Structural Phase Transitions in Caged Compounds RT2Zn20 (R = La, Pr, T = Ru, Ir) , 2010 .

[9]  F. Izumi,et al.  Three-Dimensional Visualization in Powder Diffraction , 2007 .

[10]  H. Sato,et al.  Multiband Superconductivity in Filled-Skutterudite Compounds (Pr1-xLax)Os4Sb12: An Sb Nuclear-Quadrupole-Resonance Study , 2006, cond-mat/0610215.

[11]  H. Sato,et al.  Direct observation of quadrupolar excitons in the heavy-fermion superconductor PrOs4Sb12. , 2005, Physical review letters.

[12]  H. Sugawara,et al.  Novel Kondo Behaviors Realized in the Filled Skutterudite Structure , 2005 .

[13]  E. Bauer,et al.  Superconductivity and heavy fermion behavior in PrOs 4 Sb 12 , 2002 .

[14]  W. Jeitschko,et al.  Ternary Rare Earth Transition Metal Zinc Compounds RT2Zn20 with T = Fe, Ru, Co, Rh, and Ni , 1997 .