Effect of chemical and physical pressure on the superconducting properties of LaZn_2-xSn₂

The new series of rare earth intermetallic compounds with composition RZn_2-xSn₂ has been recently discovered for the light lanthanides (R=La,Ce,Pr,Nd,Sm). Their crystal structure is a derivative of the CaBe₂Ge₂-type (tP10, P4/nmm). Single crystal structural refinements revealed defects and disorder in the structure of these compounds, with Zn-site vacancies and mixed Zn/Sn atomic occupations leading to a stoichiometry of ≈ RZn_1.5Sn₂. Physical property measurements have shown appearance of superconductivity for the La homologue, with T_c ≈ 5.5 K. This observation is unexpected in heavily disordered phases. In present work we have investigated the effect of chemical pressure brought about by atomic substitution of Zn and Sn with other properly chosen elements (Mg, Cu and Cd for Zn and In, Ge and Pb for Sn). The results will be discussed and compared with the effects of physical pressure on the superconducting properties of this material. LaZn_1.5Sn₂ represents a pristine compound for a new series of superconducting materials.
Research at Ames Laboratory is supported by the Office of the Basic Energy Sciences, Materials Sciences & Engineering Division of the US Department of Energy. Ames Laboratory is operated for the US DOE by Iowa State University under Contract DE-AC02-07CH11358.