The static and dynamic magnetic properties, electrical resistivity, specific heat, and magnetoresistance have been studied in ${\text{EuCu}}_2{\text{Si}}_2$ 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 ${\text{Eu}}^{2+}$ 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 ${\text{EuCu}}_2{\text{Si}}_2$ 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.

• Received 21 January 2008

DOI:https://doi.org/10.1103/PhysRevB.78.064409