Coexistence of long range magnetic order and intervalent state of Eu in EuCu$_{2}$(Si$_{x}$Ge$_{1-x}$)$_{2}$: evidence from neutron diffraction and spectroscopic studies

Experimental results of the $X$-ray absorption spectroscopy, Mössbauer spectroscopy (isomer shift) and neutron diffraction are presented for the series of EuCu$_{2}$(Si$_{x}$Ge$_{1-x}$)$_{2}$ polycrystalline samples ($0<x<0.75$). Homogeneous intermediate valence state is established for Eu-ions as well as long range magnetically ordered state at the temperatures below 10–15 K. Observation of the ordered magnetic moments at Eu site gives rise to the experimental statement for the coexistence of valence fluctuations and long range magnetic order takes place in the wide range of Ge concentrations for this substance.