ESR STUDY OF THE ELECTRONIC-PROPERTIES OF TERNARY EUROPIUM PNICTIDES

We report on an X-band ESR study performed together with dc susceptibility measurements of the ternary europium-transition element-pnictides EuNiP, EuPtP and EuPdAs, which show temperature-dependent mixed valency of Eu and also of EuCuP and EuAuSb with Eu ions in a temperature-independent valence state close to 2 +. The analysis of the temperature dependences of the Eu2+ ESR line parameters and especially of the Korringa contribution to the total linewidth give us reason to believe that for compounds with those transition elements which form a partially unfilled d-band (Ni, Pd, Pt) the total density of states at the Fermi level is strongly enhanced and possibly also a hybridization with the Eu-derived d-states takes place. Together, the data support the idea that strong d-character of a conduction band favours the increase in the mean valency of Eu.