Interplay between Kondo-like behavior and short-range antiferromagnetism in EuCu2Si2 single crystals

The static and dynamic magnetic properties, electrical resistivity, specific heat, and magnetoresistance have been studied in EuCu2Si2 single crystals grown by a floating zone method. The magnetic susceptibility exhibits a considerable anisotropy and a steep rise below 10 K for external fields parallel to the c axis but with no evident magnetic ordering in the temperature range of 2–350 K. The data imply a gradual change in the Eu valence as a function of temperature. Electron spin resonance (ESR) measurements reveal a sizeable fraction of stable Eu2+ magnetic moments that interact with conduction electrons and develop quasistatic antiferromagnetic correlations on the ESR timescale. The electrical resistivity and specific heat demonstrate the presence of spin fluctuations and Kondo-like behavior, which apparently competes with the antiferromagnetic order. The analysis of experimental data enables to conclude that the remarkable diversity of the physical properties of EuCu2Si2 results from the variation of lattice parameters as well as of local crystal chemistry as a consequence of the particular preparation route employed for the growth of single crystals and polycrystals.