EPR spectra of Cr³⁺ ion in the Van Vleck paramagnet EuAl₃(BO₃)₄

Abstract

Abstract We have presented new results on the EPR spectra and the ground state of the Cr 3+ ion replacing Y 3+ in YAl 3 (BO 3 ) 4 and Eu 3+ in EuAl 3 (BO 3 ) 4 single crystals. The EPR studies performed at frequencies of about 9.4 and 37 GHz in a temperature range of 300–4.2 K have revealed the peculiarities and differences of EPR spectra of Cr 3+ ion as well as determined the spin‐Hamiltonian parameters ( g ‐factors, D , and E fine‐structure parameters and their signs) in both crystals. The value and sign of the D parameter in both crystals are determined by both the nearest ligands around the Cr 3+ ion and the spin–orbit interaction. The interaction between Cr 3+ ion and rare‐earth ion weakly influences on the ground‐state splitting, while the changes of g ‐factors are mainly caused by the Cr 3+ and Eu 3+ ions interactions. The EPR spectra and contributions determining the value of spin‐Hamiltonian parameters were analyzed on the basis of the superposition model of the crystal field.