Influence of the Pd-Si ratio on the valence transition in EuPd$_2$Si$_2$ single crystals

Abstract

Single crystals of intermediate valent EuPd$_2$Si$_2$ were grown from an Eu-rich melt by the Bridgman as well as the Czochralski technique. The chemical and structural characterization of an extracted single crystalline Czochralski-grown specimen yielded a slight variation of the Si-Pd ratio along the growth direction and confirms the existence of a finite Eu(Pd$_{1-m}$Si$_m$)$_2$Si$_2$ homogeneity range. The thorough physical characterization carried out on the same crystal showed that this tiny variation in the composition affects the temperature $T_v$ at which the valence transition occurs. These experiments demonstrate a strong coupling between structural and physical properties in the prototypical valence-fluctuating system EuPd$_2$Si$_2$ and explain the different reported values of $T_v$.