Driving the europium valence state in $\mathrm{EuCo_{2}As_{2}}$ by external and internal impact

The pressure effect on the europium valence state was investigated by means of X-ray absorption spectroscopy in the series of samples based on the EuCo$_2$As$_2$ compound. The pressure dependence of the europium valence was obtained in a wide range of applied and chemical pressures; the latter was reached by substituting Ca for Eu. The correlation between these two ways to impact the Eu valence was established. The data obtained allow estimating the pressure effect on the electronic structure of EuCo$_2$As$_2$ and other related properties such as the change in magnetic ordering